John Rusnak, Allfirst Financial
A currency trader at Allfirst Financial, Rusnak lost $691 billion, mostly by betting big on the Japanese yen, increasing his positions, and hiding his losses over five years. Rusnak pleaded guilty in 2002 and served nearly six years in prison. Allfirst, which had been owned by Allied Irish Banks, was sold to the M&T Bank Corporation of Buffalo after the scandal broke.
