Who was the most self-destructive in their careers?

[Beanflicker]

Roberto Duran and James Toney deserve mentions for eating their way into weight divisions they had no business fighting in, and putting on the occasional shitty performance from being under trained.

How about George Foreman for fighting the stupidest fight possible against Ali?

Hindsight is 20/20. Here you are, a young man, a guy who blasted Ali's conquerers like Frazier and Norton out in 2 rounds, the HW champ of the world, A-level fighters disintegrating under your fists, and now you're fighting a former champ in his 30s, a guy who everyone says is well past his prime, who's had life and death battles with Ken Norton where he's had his jaw completely shattered... knowing all that you'd probably be pretty confident you can blast this old guy out in a few rounds like everyone else.