Who was the most self-destructive in their careers?

[Master]

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?

He fought stupid most of his fights but very few could take the power.

Benn did the same thing when he fought Watson.