One of the reasons I love boxing is that it's a sport where the competitors show incredible grit and determination. Obviously, many sports have their share of astonishing comebacks and contestants with incontestable heart. But there is very little that compares to the sheer willpower and desire it takes to comeback from being so hurt that you literally can't stand-up, throwing back, and winning a fight.
The first matchup between Diego Corrales and Jose Luis Castillo is considered an all-time classic, and the 10th round, shown here, is arguably one of the greatest rounds of all time. Corrales had always been a never-say-die sort of fighter -- in fact, he lost his undefeated record to Floyd Mayweather, who knocked him down 5 times across the course of the fight. When his corner finally stopped it after knockdown #5, Corrales, who was hopelessly behind and being battered pillar to post, was visibly furious.
This second one is a little macabre -- just warning. But though it shows a different sort of "comeback", I think it falls into the same category -- a demonstration of an indomitable will to win which I don't think has parallel in any other sport.