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Largest Mergers in History: Price Paid vs Value Kept

AOL paid about $165 billion for Time Warner and wrote off roughly $99 billion of it within two years, while Exxon paid $81 billion for Mobil and wrote off essentially nothing.

  • No. 1: AOL–Time Warner (2000)
  • 10 places

01Final list

The leading AIs each built their own list of ten independently. Here is one result that is easy to check: every place has a reason, a source, and the list of AIs that included it.

Order: from most to least AI agreement.

A bright badge means this AI put the entry on its list. A dim badge means it did not.

  1. 1

    AOL–Time Warner (2000)

    AOL paid about $165B. About $99.7B of goodwill was written off in 2002, roughly 60% of the price, producing a $98.7B annual loss. The companies separated again in 2009.

    Included it: Claude, Gemini, Nova, DeepSeek. Did not include: Meta, Wenxin.

    In their lists: Claude: 1 · Gemini: 10 · Nova: 2 · DeepSeek: 9

    What each AI noted 4
    • Claudeplace 1

      About $99.7B of goodwill was written off in 2002, the largest annual loss of any public company ever, and the merger was fully unwound nine years later.

      Source ↗
    • Geminiplace 10

      Paid $165 billion in overvalued dot-com equity, only to book a record $99 billion impairment in 2002 before spinning AOL off for pennies.

      Source ↗
    • Novaplace 2

      $165B; unwound in 2009 after $99B write-down

    • DeepSeekplace 9

      $99B written off, about 60% of the price; the combined market value fell from $226B to roughly $20B.

      Source ↗
    4 AIs put it here
    Source ↗
  2. 2

    Exxon–Mobil (1999)

    $81B ($76.3B at signing), and the deal that held. Pooling accounting booked no goodwill, so there was nothing to write off. Five-year return is disputed: +38% in total vs about 20% a year.

    Included it: Claude, Gemini, Nova, DeepSeek. Did not include: Meta, Wenxin.

    In their lists: Claude: 9 · Gemini: 1 · Nova: 6 · DeepSeek: 1

    What each AI noted 4
    • Claudeplace 9

      The deal held together as one company, but I found no sourced post-merger write-down or share-versus-sector figure.

      Source ↗
    • Geminiplace 1

      Paid $81 billion and wrote down $0 in goodwill, generating hundreds of billions in cumulative free cash flow over its first five years.

      Source ↗
    • Novaplace 6

      $81B; synergies realized

    • DeepSeekplace 1

      The $81B deal that actually worked: no material goodwill write-down, and roughly 20% average annual shareholder returns in the five years after.

      Source ↗
    4 AIs put it here
    Source ↗
  3. 3

    AT&T–Time Warner (2018)

    AT&T paid $85.4B in 2018 ($108.7B with debt). Four years later WarnerMedia left in a $43B spin-merger with Discovery, so roughly half the price was gone.

    Included it: Claude, Gemini, Nova, DeepSeek. Did not include: Meta, Wenxin.

    In their lists: Claude: 3 · Gemini: 8 · Nova: 8 · DeepSeek: 7

    What each AI noted 4
    • Claudeplace 3

      AT&T gave WarnerMedia away in a $43B spin-merger with Discovery about four years after buying Time Warner, and its shareholders kept 71% of the new company.

      Source ↗
    • Geminiplace 8

      Bought media for $85.4 billion in 2018 and ejected it four years later at a $47 billion haircut to merge into Warner Bros. Discovery.

    • Novaplace 8

      $108B; cultural clashes

    • DeepSeekplace 7

      $85B paid, $43B back four years later: roughly half the purchase price gone, with $38.8B of goodwill on the books.

      Source ↗
    4 AIs put it here
    Source ↗
  4. More about the top three ↓
  5. 4

    Vodafone–Mannesmann (2000)

    The largest deal ever, at $183–203B depending on the source. Vodafone wrote off £23.5B in 2006, £19.4B of it for Mannesmann. That came six years after closing, just outside the five-year window.

    Included it: Claude, Gemini, Nova, DeepSeek. Did not include: Meta, Wenxin.

    In their lists: Claude: 2 · Gemini: 9 · Nova: 1 · DeepSeek: 10

    What each AI noted 4
    • Claudeplace 2

      Vodafone wrote £23.5B off its books in 2006. Germany took £19.4B of that, and Vodafone had paid about £100B for Mannesmann at the market peak.

      Source ↗
    • Geminiplace 9

      The $180 billion hostile conquest secured Europe's mobile crown, then delivered history's largest one-year corporate write-down of £28 billion ($49 billion) in 2006.

    • Novaplace 1

      $202.8B ($397.8B adjusted for inflation)

    • DeepSeekplace 10

      $202.8B at the top of the telecom bubble; £23.5B written off and 60% of Vodafone’s value gone within two years.

    4 AIs put it here
    Source ↗
  6. 5

    AB InBev–SABMiller (2016)

    $103–107B depending on the source. AB InBev booked $72.4B of goodwill and the filings checked show none written off. Claims of African write-downs and a 46% share drop have no source.

    Included it: Claude, Gemini, Nova, DeepSeek. Did not include: Meta, Wenxin.

    In their lists: Claude: 10 · Gemini: 7 · Nova: 5 · DeepSeek: 5

    What each AI noted 4
    • Claudeplace 10

      Management found no goodwill impairment trigger on $72.4B of acquired goodwill, and total impairments in 2017 were just $6M.

      Source ↗
    • Geminiplace 7

      Brewed a $104 billion brewing monopoly but slashed its dividend twice by 50% and suffered a 46% stock plunge under $100 billion of debt.

      Source ↗
    • Novaplace 5

      $107B; required brand divestitures

    • DeepSeekplace 5

      $107B and $74B of goodwill; the cost cuts arrived, but AB InBev’s shares underperformed the global beverage index.

      Source ↗
    4 AIs put it here
    Source ↗
  7. 6

    Pfizer–Warner-Lambert (2000)

    $90B (the first hostile bid was $82.4B) bought Lipitor with no major write-down. Pfizer's shares fell about 13.5% yet still beat the drug-industry index by about 4 points.

    Included it: Gemini, Nova, DeepSeek. Did not include: Claude, Meta, Wenxin.

    In their lists: Gemini: 3 · Nova: 3 · DeepSeek: 2

    What each AI noted 3
    • Geminiplace 3

      Spent $90 billion in a hostile duel to secure Lipitor, which returned $130 billion in lifetime sales despite $8.2 billion in post-merger integration costs.

      Source ↗
    • Novaplace 3

      $90B; Lipitor integration success

    • DeepSeekplace 2

      $90B bought Lipitor, the best-selling drug in history; Pfizer kept the value even as its own shares lagged the industry.

      Source ↗
    3 AIs put it here
    Source ↗
  8. 7

    Dow–DuPont (2017)

    A $130B 'merger of equals', a figure for combined value rather than a price paid. It was built to split into three companies, and a $4.6B agriculture charge hit within a year.

    Included it: Claude, Gemini, DeepSeek. Did not include: Meta, Nova, Wenxin.

    In their lists: Claude: 4 · Gemini: 6 · DeepSeek: 4

    What each AI noted 3
    • Claudeplace 4

      The 'merger of equals' was built to be split into three companies, and a $4.6B charge on the agriculture unit hit within a year of the merger closing.

      Source ↗
    • Geminiplace 6

      A $130 billion industrial marriage formed only to be split into three companies within 24 months, absorbing $5.1 billion in pre-breakup charges.

    • DeepSeekplace 4

      $130B merger, then a three-way breakup: $1.2B of goodwill impairment and a 42% total return that trailed both the S&P 500 and the chemical index.

    3 AIs put it here
    Source ↗
  9. 8

    Verizon–Vodafone (Verizon Wireless buyout, 2013–14)

    Verizon paid $130B for Vodafone's 45% of Verizon Wireless and took no write-down on the stake. Sources disagree on returns: one says it beat telecom stocks, another that it lagged the S&P 500.

    Included it: Gemini, DeepSeek. Did not include: Claude, Meta, Nova, Wenxin.

    In their lists: Gemini: 2 · DeepSeek: 6

    What each AI noted 2
    • Geminiplace 2

      The $130 billion cash-and-stock buyout recaptured 100% of America's most profitable mobile cash generator without a single dollar of wireless impairment.

      Source ↗
    • DeepSeekplace 6

      $130B for the 45% of Verizon Wireless Vodafone did not own: no goodwill write-down, but Verizon’s stock lagged the S&P 500.

    2 AIs put it here
    Source ↗
  10. 9

    RBS consortium–ABN Amro (2007)

    The €71B (about $100B) consortium takeover broke the bank that led it. RBS wrote off £16.9B of goodwill, lost £24.1B in 2008, and the UK state took 70%.

    Included it: DeepSeek. Did not include: Claude, Meta, Gemini, Nova, Wenxin.

    In their lists: DeepSeek: 8

    What each AI noted 1
    • DeepSeekplace 8

      £16.9B goodwill write-off, a £24B loss and 70% state ownership: the consortium deal that helped break a bank.

      Source ↗
    1 AIs put it here
    Source ↗
  11. 10

    United Technologies–Raytheon (RTX, 2020)

    About $121B on one list, so treat the size as an estimate. Carrier and Otis were spun off when the merged company was formed, and a roughly $3B Pratt & Whitney engine charge followed in 2023.

    Included it: Claude. Did not include: Meta, Gemini, Nova, DeepSeek, Wenxin.

    In their lists: Claude: 5

    What each AI noted 1
    • Claudeplace 5

      Carrier and Otis were separated at the same moment the merged company was created, and a roughly $3B engine charge followed in 2023.

      Source ↗
    1 AIs put it here
    Source ↗

02More about the top three

The ranking is above. Here is more about the three places at the top: what they are, why they are here, and what is worth knowing.

The three deals are measured on different bases: AOL's loss is a 2002 accounting write-off, Exxon–Mobil had no goodwill to write off, and AT&T's loss is the gap between price and the 2022 spin-merger value.

1AOL–Time Warner (2000)

No. 1 — AOL–Time Warner (2000). On the lists of 4 of 6 AIs; median place there: 5.5. The AIs put it first because about $99B of its roughly $165B price was written off in 2002, and the merger was undone in 2009.

Did you know

  • Guinness World Records lists the AOL Time Warner write-down as the greatest annual loss by a company. About $99 billion was written off in 2002 as the dot-com crash hit AOL's subscribers and revenue. It was an accounting charge, not cash spent.

    Source ↗ ✓ confirmed by several AIs
What it is
AOL bought Time Warner in 2000 in the biggest stock deal of the dot-com boom.
Its edge
It lost the most: about 60% of the price was written off.
Who should know
Useful to know for anyone who wants to see how a merger can destroy value.
  • Price paid vs written off$99.7B written off, ~60% of price

Wikipedia · Wikidata

Why it is here

  • AOL Time Warner reported a 2002 loss of $98.7 billion. Guinness lists it as the greatest annual loss by a company. That is far bigger than the write-downs in the other two deals on this list.

    Source ↗

  • AOL paid $166 billion for Time Warner in 2000. PBS says a $45 billion write-down came on top of an earlier $54 billion one, $99 billion in total, the largest recorded write-down in U.S. corporate history.

    Source ↗
Keep in mind

  • Case blamed clashing company cultures and a power struggle with CEO Jerry Levin. The page presents this as Case's own account in his book, not independent reporting.

    Source ↗

  • Case said some shareholders blamed him personally for the weak results after the merger. That is why he left his post as AOL Time Warner chairman. He stayed on the board.

    Source ↗
Where to go further

  • Open the 2002 annual report (Form 10-K). Look at the statement of operations for the goodwill charge and the net loss. It shows how much of the merger's value was written off in one year.

    Source ↗

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Compare the top three ↓

2Exxon–Mobil (1999)

No. 2 — Exxon–Mobil (1999). On the lists of 4 of 6 AIs; median place there: 3.5. The AIs put it here because the $81B deal held together as one company, and pooling accounting left no goodwill to write off.

Did you know

  • Exxon and Mobil were once part of the same company. In 1911 the US Supreme Court broke up Standard Oil. Exxon descends from the New Jersey piece and Mobil from the New York piece, so the 1999 merger brought two relatives back together.

    Source ↗
What it is
Two giant oil companies joined in 1999 to form ExxonMobil.
Its edge
It kept its value: nothing was written off and the company was never split.
Who should know
Useful to know for anyone who wants an example of a merger that lasted.
  • Price paid vs written off$81B paid, nothing written off

Wikipedia · Wikidata

Why it is here

  • The Exxon–Mobil merger took effect on Nov. 30, 1999. The Motley Fool calls its $81 billion value the largest merger in American history at that time. It is the only one of the three that was never split apart.

    Source ↗

  • Regulators required the companies to sell over 2,400 service stations. About a year after the merger, ExxonMobil reached a $300 billion market value. The merged company kept growing instead of being broken up.

    Source ↗ ✓ confirmed by several AIs
Where to go further

  • Read the 1999 annual report (Form 10-K) filed after the merger. Start with the merger description, then the accounting notes on how the deal was recorded. That shows why no goodwill was booked.

    Source ↗
Gemini, DeepSeek put it first. What they saw in it

  • Gemini: Paid $81 billion and wrote down $0 in goodwill, generating hundreds of billions in cumulative free cash flow over its first five years.

  • DeepSeek: The $81B deal that actually worked: no material goodwill write-down, and roughly 20% average annual shareholder returns in the five years after.

Video: History of Pakistan # 43 | Nawaz Sharif vs Pervez Musharraf 1999 | Faisal Warraich · Dekho Suno Jano

Compare the top three ↓

3AT&T–Time Warner (2018)

No. 3 — AT&T–Time Warner (2018). On the lists of 4 of 6 AIs; median place there: 7.5. The AIs put it third because AT&T paid $85.4B and about four years later gave WarnerMedia away in a $43B deal, losing roughly half.

2018 год и ёлка на фоне здания на Лубянке ночью 29 декабря 2017 года (cropped)
Brateevsky · CC BY-SA 4.0 · Wikimedia Commons

Did you know

  • The US Justice Department sued in November 2017 to block the deal. It was the first federal attempt in nearly 40 years to break apart a vertical merger. A judge ruled for AT&T in June 2018, and the deal closed two days later.

    Source ↗ ✓ confirmed by several AIs
What it is
AT&T bought Time Warner in 2018, then spun WarnerMedia off in 2022.
Its edge
It was reversed faster than AOL's deal, in under four years.
Who should know
Useful to know for anyone who wants to see a quick reversal after a court fight.
  • Price paid vs written off$85.4B paid, $43B back

Wikipedia · Wikidata

Why it is here

  • AT&T bought Time Warner in 2018 for $85 billion. Then WarnerMedia was merged with Discovery in a $43 billion deal. AT&T shareholders were to own 71% of the new company and Discovery holders about 29%.

    Source ↗

  • The $43 billion WarnerMedia–Discovery deal was announced in 2021, less than three years after AT&T bought Time Warner. That is a much faster reversal than AOL's, which took nine years to unwind.

    Source ↗
Keep in mind

  • Semafor says heavy debt, regulatory delays and accusations of management mistakes undid the deal. In 2022 AT&T said it would focus on its wireless networks and spun off WarnerMedia to combine with Discovery.

    Source ↗
Where to go further

  • Read the closing press release (Form 8-K) from April 2022. It explains how AT&T spun off WarnerMedia and merged it with Discovery in an all-stock deal.

    Source ↗

Video: APOSTLE (2018) Ending Explained · FoundFlix

Compare the top three ↓

The top three side by side

AOL–Time Warner (2000)Exxon–Mobil (1999)AT&T–Time Warner (2018)
In the AIs' lists4 / 64 / 64 / 6
Price paid vs written off$99.7B written off, ~60% of price$81B paid, nothing written off$85.4B paid, $43B back
Put first byClaudeGemini, DeepSeek—

Places with the same number of AIs are ordered by their average place in the AIs' own lists.

More ratings

03Worth knowing

What the AIs noticed while building the list.

AOL Time Warner's roughly $99.7B goodwill charge was about 60% of the price, and it exceeded the headline price of every other deal on this list except Vodafone–Mannesmann.

Noticed by:
Included it: Claude, Gemini, DeepSeek. Did not include: Meta, Nova, Wenxin.
Source ↗

Vodafone warned of a £23–28B impairment and took £23.5B, six years after closing. The damage showed in the share price first, and the £28B ($49B) sometimes quoted is only the top of the warning range.

Noticed by:
Included it: Claude, DeepSeek. Did not include: Meta, Gemini, Nova, Wenxin.
Source ↗

Value can be lost before the buyer takes over: AT&T took $16.5B of impairments on AT&T Broadband before Comcast closed the $72B deal.

Noticed by:
Included it: Claude. Did not include: Meta, Gemini, Nova, DeepSeek, Wenxin.
Source ↗

Just below this cut, Bristol-Myers Squibb–Celgene ($74B) left a $6.4B contingent payment to Celgene holders that expired worthless when a drug approval missed its deadline.

Noticed by:
Included it: Claude, Gemini, Nova. Did not include: Meta, DeepSeek, Wenxin.
Source ↗

04Questions people ask

What is the largest merger in history?

Vodafone's takeover of Mannesmann, agreed in February 2000. It is valued at $183B on the final offer and up to $202.8B in other counts.

What was the worst merger in history?

AOL–Time Warner is the usual answer. It wrote off about $99B in 2002, roughly 60% of the $165B price.

Source ↗
Did any of the largest mergers keep their value?

Yes. Exxon–Mobil ($81B) had no material write-down, and AB InBev booked $72.4B of goodwill from SABMiller without writing any of it off in the filings checked.

Source ↗
Why do sources give different sizes for the same merger?

Some quote the value at announcement, others at closing or including debt. AOL–Time Warner appears as $147B, $165B or $182B, and the $350B sometimes cited is the combined market value, not the price.

Source ↗

05How we counted

In plain words, no formulas.

1The question

Top 10 Largest Mergers in History: Price Paid vs. Value Kept Five Years Later

2Why this topic

Readers see each record price set against what the company later wrote off or split apart, from two separate sources: the deal tally and the company's own filings.

3Where it applies

Global corporate M&A, deals of at least $70 billion announced value

4What we looked at

  • Announced transaction value at signing (minimum $70 billion)
  • Goodwill write-downs, restructuring charges and spin-offs within five years of closing, as a share of the purchase price
  • Combined shareholder value change from announcement to five years after closing, compared with the sector index
  • Institute for Mergers, Acquisitions and Alliances (IMAA) — Announced and closed deal values for the largest global transactions; this list's order (largest first, $70B minimum)
  • Wikipedia / Smartroom lists of largest M&A — Announced deal values used to check IMAA figures; they differ by announcement, closing and debt-inclusive values
  • U.S. SEC EDGAR (10-K, 20-F) and company reports — Goodwill impairments, restructuring charges, write-offs and spin-offs after closing: what each deal kept

5Who ranked

The leading AIs, each building its own list of ten independently and naming a source for every place: Claude, Meta, Gemini, Nova, DeepSeek, Wenxin.

6How the places were set

The same entry written differently by different AIs was counted as one. The more AIs put an entry on their list, and the higher they put it, the higher its place. "AI agreement" shows how many of the AIs had it on their own list. Sources are only those the AIs found themselves; nothing was added by hand.

06Each AI's own list

🇺🇸 Claude10 places · 4 notes

The same question, answered by Claude alone. The final list above combines all the AIs.

  1. 1
    AOL–Time Warner (2000)

    About $99.7B of goodwill was written off in 2002, the largest annual loss of any public company ever, and the merger was fully unwound nine years later.

    Source ↗
  2. 2
    Vodafone–Mannesmann (2000)

    Vodafone wrote £23.5B off its books in 2006. Germany took £19.4B of that, and Vodafone had paid about £100B for Mannesmann at the market peak.

    Source ↗
  3. 3
    AT&T–Time Warner (2018)

    AT&T gave WarnerMedia away in a $43B spin-merger with Discovery about four years after buying Time Warner, and its shareholders kept 71% of the new company.

    Source ↗
  4. 4
    Dow–DuPont (2015)

    The 'merger of equals' was built to be split into three companies, and a $4.6B charge on the agriculture unit hit within a year of the merger closing.

    Source ↗
  5. 5
    United Technologies–Raytheon (2019)

    Carrier and Otis were separated at the same moment the merged company was created, and a roughly $3B engine charge followed in 2023.

    Source ↗
  6. 6
    Bristol-Myers Squibb–Celgene (2019)

    A $6.4B contingent payment to Celgene holders expired worthless after a drug approval deadline was missed, and it is still being litigated.

    Source ↗
  7. 7
    Disney–21st Century Fox (2017–2019)

    Disney booked $69.5B at closing against $52.4B at the first announcement, and the acquired Fox business lost $245M in fiscal 2020.

    Source ↗
  8. 8
    AT&T Broadband–Comcast (2002)

    AT&T took $16.5B of impairment charges on its cable unit before Comcast closed the $72B deal, so the seller wrote the price down and the buyer kept the business.

    Source ↗
  9. 9
    Exxon–Mobil (1998–1999)

    The deal held together as one company, but I found no sourced post-merger write-down or share-versus-sector figure.

    Source ↗
  10. 10
    AB InBev–SABMiller (2016)

    Management found no goodwill impairment trigger on $72.4B of acquired goodwill, and total impairments in 2017 were just $6M.

    Source ↗

What Claude noticed

AOL Time Warner's goodwill charge of about $99.7B was larger than most lists' headline price for any other deal except Vodafone–Mannesmann. It resulted in a 2002 net loss of $98.7B.

Source ↗

AT&T Broadband's $16.5B of impairment charges came on the seller's side before closing, so the largest deals can lose value before the buyer even takes control.

Source ↗

AB InBev's SABMiller goodwill was revised down by about $1.7B at the accounting stage, but it was never written off. It is the one deal here that looks like it held together on paper and in filings.

Source ↗

Vodafone warned of a £23–28B impairment in February 2006. The actual charge was £23.5B, at the low end of that range.

Source ↗
🇺🇸 Gemini10 places · 1 notes

The same question, answered by Gemini alone. The final list above combines all the AIs.

  1. 1
    Exxon and Mobil (1999)

    Paid $81 billion and wrote down $0 in goodwill, generating hundreds of billions in cumulative free cash flow over its first five years.

    Source ↗
  2. 2
    Verizon Communications and Vodafone / Verizon Wireless Buyout (2014)

    The $130 billion cash-and-stock buyout recaptured 100% of America's most profitable mobile cash generator without a single dollar of wireless impairment.

    Source ↗
  3. 3
    Pfizer and Warner-Lambert (2000)

    Spent $90 billion in a hostile duel to secure Lipitor, which returned $130 billion in lifetime sales despite $8.2 billion in post-merger integration costs.

    Source ↗
  4. 4
    GlaxoWellcome and SmithKline Beecham / GSK (2000)

    Constructed a $76 billion transatlantic pharmaceutical anchor that preserved 92% of combined capital value through disciplined integration.

  5. 5
    Bristol-Myers Squibb and Celgene (2019)

    A $74 billion bet on oncology that generated over $50 billion in post-close operating cash flow before patent expirations triggered write-downs.

    Source ↗
  6. 6
    Dow Chemical and DuPont (2017)

    A $130 billion industrial marriage formed only to be split into three companies within 24 months, absorbing $5.1 billion in pre-breakup charges.

  7. 7
    Anheuser-Busch InBev and SABMiller (2016)

    Brewed a $104 billion brewing monopoly but slashed its dividend twice by 50% and suffered a 46% stock plunge under $100 billion of debt.

    Source ↗
  8. 8
    AT&T and Time Warner (2018)

    Bought media for $85.4 billion in 2018 and ejected it four years later at a $47 billion haircut to merge into Warner Bros. Discovery.

  9. 9
    Vodafone AirTouch and Mannesmann (2000)

    The $180 billion hostile conquest secured Europe's mobile crown, then delivered history's largest one-year corporate write-down of £28 billion ($49 billion) in 2006.

  10. 10
    AOL and Time Warner (2001)

    Paid $165 billion in overvalued dot-com equity, only to book a record $99 billion impairment in 2002 before spinning AOL off for pennies.

    Source ↗

What Gemini noticed

The record for the largest corporate accounting write-down in world history belongs to AOL Time Warner ($98.7B in 2002), closely followed by Vodafone's Mannesmann write-down (£28B in 2006).

Source ↗
🇺🇸 Nova10 places

The same question, answered by Nova alone. The final list above combines all the AIs.

  1. 1
    Vodafone – Mannesmann (1999)

    $202.8B ($397.8B adjusted for inflation)

  2. 2
    AOL – Time Warner (2000)

    $165B; unwound in 2009 after $99B write-down

  3. 3
    Pfizer – Warner-Lambert (2000)

    $90B; Lipitor integration success

  4. 4
    Daimler-Benz – Chrysler (1998)

    $36B; sold for $7.4B in 2007

  5. 5
    AB InBev – SABMiller (2015)

    $107B; required brand divestitures

  6. 6
    Exxon – Mobil (1998)

    $81B; synergies realized

  7. 7
    Glaxo Wellcome – SmithKline Beecham (2000)

    $107B; created GSK

    Source ↗
  8. 8
    AT&T – Time Warner (2016)

    $108B; cultural clashes

  9. 9
    Bristol-Myers Squibb – Celgene (2019)

    $89B; oncology focus

  10. 10
    Charter – Time Warner Cable (2016)

    $79B; debt-heavy

🇨🇳 DeepSeek10 places · 3 notes

The same question, answered by DeepSeek alone. The final list above combines all the AIs.

  1. 1
    Exxon–Mobil (1999)

    The $81B deal that actually worked: no material goodwill write-down, and roughly 20% average annual shareholder returns in the five years after.

    Source ↗
  2. 2
    Pfizer–Warner-Lambert (2000)

    $90B bought Lipitor, the best-selling drug in history; Pfizer kept the value even as its own shares lagged the industry.

    Source ↗
  3. 3
    AT&T–BellSouth (2006)

    $86B and a 29.8% cumulative return around the deal: the wireless crown jewel paid for itself.

    Source ↗
  4. 4
    Dow–DuPont (2017)

    $130B merger, then a three-way breakup: $1.2B of goodwill impairment and a 42% total return that trailed both the S&P 500 and the chemical index.

  5. 5
    Anheuser-Busch InBev–SABMiller (2016)

    $107B and $74B of goodwill; the cost cuts arrived, but AB InBev’s shares underperformed the global beverage index.

    Source ↗
  6. 6
    Verizon–Vodafone (2013)

    $130B for the 45% of Verizon Wireless Vodafone did not own: no goodwill write-down, but Verizon’s stock lagged the S&P 500.

  7. 7
    AT&T–Time Warner (2018)

    $85B paid, $43B back four years later: roughly half the purchase price gone, with $38.8B of goodwill on the books.

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  8. 8
    RBS consortium–ABN Amro (2007)

    £16.9B goodwill write-off, a £24B loss and 70% state ownership: the consortium deal that helped break a bank.

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  9. 9
    AOL–Time Warner (2001)

    $99B written off, about 60% of the price; the combined market value fell from $226B to roughly $20B.

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  10. 10
    Vodafone–Mannesmann (2000)

    $202.8B at the top of the telecom bubble; £23.5B written off and 60% of Vodafone’s value gone within two years.

What DeepSeek noticed

AOL’s $99B write-off was about 60% of the $165B price — the largest accounting admission that a mega-merger had destroyed value.

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Exxon–Mobil is the outlier: $81B, no material goodwill impairment, and roughly 20% average annual shareholder returns in the five years after.

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The “top 10” changes with the metric: by announced value Vodafone–Mannesmann leads at $202.8B; by write-down share AOL leads at roughly 60%.

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