On November 25, 1980, at the Superdome in New Orleans, Sugar Ray Leonard won the WBC welterweight title when his opponent Roberto Duran surprised the world by throwing in the towel in the eighth round. Duran had taken the title from Leonard six months earlier in a brawl in Montreal that would take 15 rounds for him to win by unanimous decision. That wasn't the case in New Orleans. Leonard controlled the fight from beginning to end. Duran claimed that he started experiencing stomach cramps in the fifth which led him to telling the referee "no mas, no mas" in the eighth round. Leonard looked slightly stunned by his decision to call it quits as he lifted his arms in the air before jumping up on the ropes in celebration.Many thought that 29 year old Duran was simply getting beat so handedly that he just gave up to the 24 year old Leonard. Some said that Duran lost heart, his own trainer said he quit because he was embarrassed. It was a crushing blow for Duran who contemplated retirement after the fight. Although, his career would continue after a two year hiatus from the sport and would even fight Leonard 10 years later. Once again Leonard would get the best of him and win by unanimous decision.
You can watch the fight here: https://www.youtube.com/watch?v=x7aChC6U3Ks