This was supposed to be the year that Ken Lewis, the outsider who rose to the pinnacle of American banking, finally conquered Wall Street. He will resign instead.

The Bank of America Corp. (BAC) chief executive did complete the empire that his predecessor as CEO, Hugh McColl Jr., started to build with the merger of BankAmerica and NationsBank. But Lewis's completion of that empire came at a high cost to shareholders, and ultimately to himself.

When Lewis, 62 years old, resigns at the end of the year, he will end a remarkable career in banking tarnished by questions from regulators and Wall Street about his handling of the last building block to the Bank of America he envisioned: The acquisition of Merrill Lynch & Co.

Lewis was born in Mississippi and raised by a single mother with modest means, a fact that he often said formed his life and his career. He won the American Banker's "Banker of the Year" award twice, including last year. At the ceremony, he said: "This is not a time for celebration in our industry."

Humility was unusual for Lewis, who was accustomed to making bets, and to winning. In 2004, he boldly bought FleetBoston Financial at a price that shocked investors - Bank of America's stock price sank. But by most accounts, the deal paid off. He was confident that Bank of America could repeat the strategy with the acquisition of credit card lender MBNA Corp., and troubled mortgage lender Countrywide Financial last year just before Wall Street fell into a shocking tumble. He had also acquired U.S. Trust Co., an upscale bank, and LaSalle Bank in Chicago - building a massive consumer lender.

It seemed Lewis envisioned Bank of America as a bank, not a titan of Wall Street. In 2007, after reporting losses in BofA's modest investment-banking division, he told investors: "I've had all the fun I can stand" in investment banking.

But it was Merrill Lynch that turned out to be his biggest bet. In a deal drawn up over a dramatic weekend that ended in the collapse of Lehman Brothers, Lewis once again made a bold move: He paid a hefty $29 per share for Merrill, which was also believed to be close to suffocation.

Finally, Bank of America was truly a universal bank, and viewed itself as peer to Wall Street powerhouse JPMorgan Chase & Co. (JPM). Shortly thereafterwards, however, Bank of America appeared more like Citigroup Inc. (C): a bank struggling with massive losses that illustrates the kind of credit risk that management underestimated.

Such suggestions angered Lewis, who defended his acquisition of Merrill Lynch. He argued that Merrill's sheer earnings power will vindicate him, just as the earnings power of Fleet confirmed Lewis' vision of building a massive retail bank. JPMorgan Chase and Wells Fargo & Co (WFC) have since caught up with BofA in deposits and branches.

Lewis became CEO in 2001, succeeding the legendary McColl; he had joined Bank of America in 1969. This April, shareholders demanded the bank strip him of the chairman title, and the board complied. Bank of America announced his resignation without naming a successor.

-By Matthias Rieker, Dow Jones Newswires; 212-416-2471; matthias.rieker@dowjones.com