Citadel founder and CEO Kenneth Griffin is an unlikely hedge fund legend. He never attended business school or worked on Wall Street. Instead, he started trading convertible bonds out of his Harvard University dorm room in the late 1980s and launched Citadel in 1990 with backing from Frank Meyer of Glenwood Capital. Citadel's stellar gains quickly put the firm on the map, and its assets climbed to $20 billion in 2008. But later that year, the firm experienced a brush with death as a result of the financial crisis…