Miguel Cotto retained his WBO light welterweight crown with a ninth-round stoppage of Mohamad Abdulaev at Madison Square Garden, New York, on Saturday.
The highly-rated Puerto Rican, 24, who has already called out new IBF champion Ricky Hatton, lost badly as an amateur to Abdulaev at the Sydney Olympics.
But Cotto got his revenge 57 seconds into the ninth when Abdulaev's right eye became completely shut.
Cotto said: "He's a great athlete, but his body couldn't go on any longer."
Abdulaev beat Cotto in the opening round of the 2000 Olympics and went on to win the gold medal.
But in front of a partisan crowd in New York, the Puerto Rican was leading on all the cards when stopped.
"He still had the same style from when I fought him in the Olympics," said Cotto, who was making his third title defence.
"He was strong and came forward through the fight just as he did in the Olympics, but tonight I worked him well."
Fritz Sdunek, Abdulaev's head trainer, admitted: "He took a hard right to the eye in the sixth round.
"That's when the trouble started and even though we kept applying ice, it kept getting worse."