The G-Man Gerald McClellan.

He was a Great fighter.
Emanuel Stewart said McClellan was the most talented fighter he ever worked with.

Most boxers come from rough neighborhoods, and you can't just turn off that kind of learned behavior formed in childhood. Many boxers learn that self-discipline from Boxing, but McClellan remained a real devil outside the ring...

https://www.youtube.com/watch?v=dKlVmagg8l0