Oleksandr Usyk remained the undisputed world cruiserweight champion on Saturday with an eighth round stoppage of Tony Bellew at the Manchester Arena.
The 2012 Olympic heavyweight gold medallist stunned Bellew with a right to the head before banging in a looping left to send him crashing to the canvas and, ultimately, into retirement.
British referee Terry O'Connor stepped in and stopped the fight, with 31-year-old Usyk stretching his professional record to 16-0-0.
In a fight that was more evenly matched than most had expected, Bellew was ahead 67-66 68-65 on two of the scorecards and level 67-67 on the third going into the decisive round after coming out fighting from the start.
Usyk, the first man to hold the IBF, WBO, WBA and WBC belts simultaneously, has made no secret of the fact he wants to move up to heavyweight and challenge Britain's reigning champion Anthony Joshua.
Joshua, who holds the WBA, IBF, WBO and IBO heavyweight belts, was the 2012 Olympic super-heavyweight champion.
Former super middleweight world champion Carl Froch believes Usyk is a serious threat to the heavyweight division.
"He is a serious threat to the heavyweight division, you can say that. I would just like to say that Tony Bellew really put up a top performance, probably one of the career-best performances, but he came up against a fantastic Usyk tonight," Froch told Sky Sports.
"What a way to end his career. What a shame, but he's got a lot to be proud of, and we've really found someone in Oleksandr Usyk that is very, very special. We need to acknowledge that.
"I think because of the sheer size of him, and the fact he boxed at heavyweight as an amateur, I think he can make that transition very well, but it has to be a steady one. He needs to choose his enemies wisely early on, and then we know he's looking for big AJ, that may be too ambitious.
"You can see he's a big unit. He's backed up by a lot of muscle. He can go up comfortably and he's tall enough as well."