6. Yasuo Hamanaka (Loss: $2.62 billion)
Yasuo Hamanaka was a copper trader from the Sumitomo Corp and widely known for his aggressive trading style. In the mid 1990’s, Hamanaka performed a series of unauthorized copper trades in the London Metal Exchange resulting in a loss of $1.8 billion, revised in September 1996 to $2.62 billion. Hamanaka served seven years in prison and released in July 2005.