At the age of 77, Mr. Soros, one the world's most successful investors and richest men, leapt out of retirement last summer to safeguard his fortune and legacy. Alarmed by the unfolding crisis in the financial markets, he once again began trading for his giant hedge fund - and won big while so many others lost.

Mr. Soros has always been a controversial figure. But he is becoming more so with a new, dire forecast for the world economy. Last week he rushed out a book, his 10th, warning that the financial pain has only just begun.

"I consider this the biggest financial crisis of my lifetime," Mr. Soros said during an interview Monday in his office overlooking Central Park. A "superbubble" that has been swelling for a quarter of a century is finally bursting, he said.

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Mr. Soros has been worrying about the fragile state of the markets for years. But last summer, at a luncheon at his home in Southampton with 20 prominent financiers, he struck an unusually bearish note.

"The mood of the group was generally gloomy, but George said we were going into a serious recession," said Byron Wien, the chief investment strategist of Pequot Capital, a hedge fund.

Mr. Soros was one of only two people there who predicted the American economy was headed for a recession, he said.

Shortly after that luncheon Mr. Soros began meeting with hedge fund managers like John Paulson, who was early to predict a crisis in the housing market. He interrogated his portfolio managers and external hedge funds that manage his fund's money, and he took on new positions to hedge where they might have gone wrong. His last-minute strategies contributed to a 32 percent return - or roughly $4 billion for the year.