10. Lennox Lewis
When he walked away from boxing in 2003, Lewis had nothing left to prove. He had become undisputed heavyweight champion of the world and beaten everyone he had ever fought as a pro – including the best of the new breed (Michael Grant and David Tua) and the best of his era (Mike Tyson and Evander Holyfield).
An Olympic gold medallist in 1988, Lewis launched himself into the world scene in the paid ranks when he battered Donovan ‘Razor’ Ruddock in 1992.