Tavistock Group founder
Estimated losses: $904.5 million*
The British-born currency trader and multi-billionaire bet six months ago that Bear Stearns, which had already shed about 30% of its value, was a bargain. He scooped up enough stock to become the firm's largest shareholder, with a 9% stake by year-end.*Estimates based on Lewis' holdings at the beginning of 2008, when the stock was trading at $88.35.
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