Wladimir Klitschko gained revenge on Lamon Brewster by stopping the American in Cologne on Saturday to retain his IBF heavyweight title.
Klitschko has won 49 of his 52 fights, 43 victories coming by KO
The 31-year-old champion, making his third successful defence, won by technical knockout after Brewster, 34, failed to come out for round seven.
Two powerful left-right combinations in the sixth proved decisive.
"Brewster was tough, but there was no way I could lose," said Klitschko, who was beaten by Brewster in 2004.
Brewster had not fought since sustaining an eye injury when losing to Sergei Liakhovich in April, 2006.
His inactivity showed as he rarely troubled the Ukrainian, although he did land a good punch early in the fifth.
Wladimir beat me fair and square; I did my best, but he was on his game
But Klitschko's strong left jab caused the American plenty of problems and prompted Brewster's coach Buddy McGirt to throw in the towel before the start of round seven, upsetting some sections of the crowd in the process.
Klitschko, whose left hand was heavily bandaged at the post-fight press conference, was happy to put the most painful loss of his career behind him.
"He did not challenge me at all," he said. "I saw all of his punches coming. I had waited for this fight so long. The loss in 2004 really hurt. I was at the very bottom of my career but I came back.
The 34-year-old Brewster did not argue with McGirt´s decision to stop the fight.
"The better man won tonight," he admitted. "Wladimir beat me fair and square. I did my best, but he was on his game."
Klitschko has now won 49 of his 52 fights, with 43 knockouts, while this was the fourth defeat of Brewster's career.