(FORTUNE Magazine) – By turning once-softhearted "Mother Merrill" into a lean, mean high-margin machine--and by navigating regulatory probes of its research unit--O'Neal restored luster to one of the great names on Wall Street. His traders dominate the market as middlemen. His investment bankers are once again landing big-dollar deals. His 14,000-stockbroker army is capturing wealthy individual investors. Insiders say O'Neal, 51, is too tough. He's certainly determined. He won a brutal succession battle for CEO, has maintained close ties to key board members, and has assembled a kitchen cabinet--called the "junta" by some--that follows his commands with precision. Love him or hate him, the results speak for themselves: Merrill earned $2.5 billion in 2002 and stands to do even better this year. --D.R.