(FORTUNE Magazine) – Greenberg has been at the helm of AIG for 36 years. He built it into the world's largest insurance company: AIG's net income last year was more than that of the top 18 U.S. property-casualty firms combined. Though he's 78 now, Greenberg has hardly slowed down. In 2001 he single-handedly hung up China's entry into the WTO until he won his company an exemption on foreign-ownership rules. ("He's one of the only people who can knock on the door of the Premier of China and have the guy answer it," says an analyst.) That same year he outmaneuvered Prudential U.K. to snag life insurer American General for $23 billion. Now he's tackling the tort system, lobbying Congress to restrict the size of plaintiffs awards. Don't bet against him. --J.C.