David Haye returned after a three-and-half-year lay-off with a first-round knockout of Mark de Mori in London.
Australian De Mori looked bothered by the first jab Haye threw and thereafter it was one-way traffic.
Haye, 35, set up the finish with huge overhand right and De Mori was unconscious before he hit the canvas with 49 seconds left in the round.
Haye's stated ambition is to regain the world heavyweight crown he lost to Wladimir Klitschko in 2011.
The Londoner's last fight was a fifth-round knockout of Dereck Chisora in July 2012 and prior to Saturday he had fought only four times in five years.
He announced his retirement in 2013, having been advised not to fight again after undergoing extensive shoulder surgery.
"It's been a tough road but I'm finally back," said Haye, who now has 27 wins from 29 professional fights.
"I felt so cool and calm in there. I don't believe any heavyweight out there could have taken those punches.
"The shoulder feels better than it was before. I feel this new and improved version of me will go on and win heavyweight championships."
Judging by the 16,000 crowd at the O2 Arena, Haye's comeback certainly piqued the interest of the British public, although some of them might have felt short-changed by the fare on offer.
Before Saturday, the 33-year-old De Mori had been beaten only once in 33 professional fights but he was hopelessly outgunned by his more celebrated opponent.
One thing we did learn from the fight was that Haye's shoulder reconstruction has done nothing to quell his power, while his successful return creates further intrigue in a revitalised heavyweight division.
Klitschko lost his WBA, IBF and WBO belts to Manchester's Tyson Fury last November, although Fury has since been stripped by the IBF.
Fury has vowed he will never defend his titles against Haye after the Londoner pulled out of two scheduled bouts against him in 2013.
But if Fury defeats Klitschko in a rematch this summer and Haye puts a string of eye-catching victories together, money might begin to talk louder than words.
"I think Tyson Fury is a good fighter, very good," said Haye. "It's a shame he doesn't want to fight me. I think we all know why, when he sees punch power like that."
"I want to get back in the ring as soon as possible, keep testing myself and work up the rankings to get a title fight."
Fury watched Deontay Wilder retain the WBC heavyweight title in New York on Saturday - then traded insults with the American in the ring.
Another potential future opponent for Haye is fellow Londoner Anthony Joshua.
"I think a fight between me and Anthony Joshua will be way bigger [than a fight against Fury]," said Haye. "I believe that's a fight that could be made later in the year."
However, Joshua's team are unlikely to risk their man against a boxer of Haye's pedigree any time soon.
A more realistic short-term opponent is Dillian Whyte, who was knocked out by Joshua last month, but gave a surprisingly good account of himself.