Your choices for fighters with the strongest will to win

I was just writing about Hopkins in another thread and felt this topic might make a good thread.

What fighters do you feel have, or have had, the greatest will to win/refusal to lose in the history of boxing?

Several I can think of off the top of my head:

Rocky Marciano
Hopkins (amazing what he has come back from and to do what he's doing at his age)
Calzaghe
Sugar Ray Leonard
Vitali Klitschko
Nigel Benn

Of course, there are guys with equal wills to win who happen to be less talented than those mentioned above.

Also, there are guys who once had an incredible will to win but after suffering a setback/adversity lost that will, confidence or whatever. Examples include:

Mike Tyson
Roberto Duran (No mas)

I'm not putting Duran down. He had an unbelievable desire to win. It's just a reference point of a guy who came up against a situation that turned him from aggressor to either passive participant or guy who took a way out. In other words, someone whose will or belief in his ability to win got sapped.

Who are some of the strongest-willed guys in the sport of boxing you have ever seen?