Shot brain damaged Riddick Bowe doing MUAY THAI ? Joe Frazier's one although I don't remember the details was pretty sad too. Who else? I bet there is a lot
Kirkland Laings life went downhill pretty fast from the moment his hand was raised against Duran. Of the all time greats I'd say Sonny Liston or Joe Louis
Quarry. Quarry had brain damage and was also being filled with pills by his brother {the non-boxing one, so I guess he had the brains} to make him manageable and malleable. When Jerry had nothing left he was left to rot. He actually died of pneumonia in the end.