Probably Carl Froch. There isn't many 15 round fighters in boxing today and Froch is a guy who comes on stronger as the fight goes on.
When I think of great athletes I think of guys like Bo Jackson who could seemingly step on to any field or court and play the game and excel at it Power and strength, Speed and Agility, Coordination and Balance, Stamina and vision He was able to go pro in 2 sports and there is another guy like Russell Wilson who is a tremendous athlete Boxing I mean I haven't seen these guys do much outside of boxing I'd have to say Sergio Martinez
Seth Mitchell .... Nah I'm joking, has to be Ali, regardless if you think he is the greatest, the man was so agile for his size and moved like nobody else I've seen when he was on his toes.