TBD by Editorial
Focus on Sport/Getty Images

George Foreman

1973-74; 1994-97

Foreman, a 1968 Olympic gold medal winner for the U.S., had won all 37 of his first professional fights when he challenged Joe Frazier for the title in Kingston, Jamaica, in 1973. The scowling, hammer-fisted Foreman dropped Frazier a total of six times in the first two rounds ("Down goes Frazier!" barked Howard Cosell) before the fight was stopped and Foreman had a TKO -- and the championship.

Foreman lost the title to Muhammad Ali after two defenses and, in 1977, retired for a decade. "Big George" returned to win his first 24 post-retirement bouts and later, a full 20 years after previously holding the title, shocked Michael Moorer with a one-punch 10th-round knockout to win it back again.