Biggest Underachiever?

One that definitely comes to mind is David Tua. I thought at the beginning of Tua's career, that he had the physical tools to maybe become the next Mike Tyson. Boy, was I ever wrong? Also you can't leave Zab out of this. Zab, as I believe Larry Merchant or Lampley once put it: Suffers from the curse of the gifted. Meaning he tried to win too many fights on his reflexes, without using basic boxing fundamentals. He also never managed to work out his footwork. I can't count the times Zab got caught because his feet were too close together. Surely Zab has learned by now when you fight orthodox fighters, you need to keep your right foot on the outside of his left?