Grant crossed my mind too, but if you think about it, he wasn't all that talented boxing-wise, just huge and athletic. Not really a surprise that he didn't pan out.
Iron Mike Tyson. I have him at #9 all time. With what he had, #1 was within his grasp. He could have been the best that ever did it and didn't make it. In my eyes that makes him a bigger waste than the others that have been mentioned.
Perhaps the most naturally talented heavyweight I have ever seen was Corrie Sanders. He was a southpaw, his punches were extremely fast, with tons of leverage. Everything came at you backwards and you could not see his straight left coming. Because of the boycott of South Africa, he was not allowed to fight for the gold medal, could have won it easily, also could have been a pro world champion for years, if only he had trained. His best weight was only 225, yet that was so damned deceptive, his height and reach was very excellent, but he was so damned quick. His nickname was "Sniper" for good reason. I followed his career for many years, could have been so damned good! Hell, I have seen his fight at his best.
Yes, he was a waste of talent. Bad management. Cooney was a two time winner of the golden gloves/NY, as a middleweight and a heavyweight. He could punch very hard. However, he was not anywhere nearly as good as Corrie once was.
Oh, I believe it was George Chaplan who said that the hardest he had ever been punched was by one of Ali's right hands, (underrated power) and by Cooney's left hook...and he should know.
Waste of talent? Ibeabuchi for sure is the number one, he trully flushed it down the toilet. Maybe Tommy Morrison can be mentioned as a waste. As pros, Felix Savon and Teofilo Stevenson were huge wastes of talent. The rest of the guys mentioned are all underachievers, who had their moment at the spotlight, but could have donne a lot more. Underachievers: Tyson Tua Golota Bowe Foreman Vitali McCall Gomez Mesi Audley Harrison
I was in Bowe's camp years ago w/ Eddie Futch. (Papa Smurf) He really became angry with Bowe for not working to his full potential. The Golota fight ended Bowe's career, Futch was not with him in the rematch and for good reason. Futch was one of the truly great trainers. However, Bowe did become champion, so get got more than some.
No Tyson underachieved but he still did enough to be a lower top 10 ATG. Bowe is the far bigger underachiever.