Sergey Kovalev of Russia dominated Bernard Hopkins from the opening bell, winning a unanimous decision early on Sunday to stake his claim as the world's best light heavyweight.
Kovalev has three versions of the 175-pound belt after taking two from the 49-year-old Hopkins in the decisive victory.
He is now 26-0-1 with 23 knockouts.
Kovalev received winning scores of 120-107 from two judges and 120-106 from the third. The 31-year-old Russian won the IBF and WBA light heavyweight belts to go with his own WBO title.
Two months shy of 50, Hopkins (55-7-2) could face retirement after a rare title bout where he was never a factor.
Kovalev knocked down Hopkins in the first round and never backed off his punishing pace.
He wanted the KO and battered his opponent against the ropes in the 12th, making the Philadelphia fighter at last look his age.
But did it bring Hopkins to his professional end?
"I really don't want to say anything," Hopkins said. "It's been 50-50 for the last nine years."