Hagler, known for his ominous shaven skull and workmanlike demeanor, was a well-rounded boxer/puncher who held the undisputed middleweight crown from 1980 to 1987 making 12 straight title defenses. Born Marvin Hagler, he legally changed his name to add the "Marvelous" in 1982.

Hagler will always be remembered along with Roberto Duran, Thomas Hearns and Sugar Ray Leonard, whom he lost his title to in a controversial 1987 split decision, as part of the "four kings" who dominated and revived the sport of boxing in the 1980s. His third round knockout of Hearns in 1985 is considered one of the most thrilling fights in boxing history.