Deontay Wilder looked down and out nearing the end of the seventh round of his WBC Heavyweight World Title defence against Luiz Ortiz.
Ortiz has dominated throughout the fight and looked to be cruising towards a huge points victory.
But one punch can change everything and this fight was no different with Wilder dropping Ortiz with a savage right hand that floored Ortiz.
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The punch was so savage, it left the referee with no choice but to call off the fight.
Wilder was gracious in victory and paid tribute to his opponent.
"You can see why no other heavyweight wants to fight Ortiz," Wilder said. "He's very crafty in the ring and he moves strategically. I had to play around with him and measure him in certain places. I had to go back and go forward. My intellect is very high although I don't get credit for it. I finally found my measurement and I took the shot and I hurt him."
It makes Wilder the sixth heavyweight in history with 10 straight trtle defences, tying Muhammad Ali.
Wilder confirmed the sequel fight with Tyson Fury in February and is then looking for a unification bout.
"Next, of course, we have the rematch with Tyson Fury," he said. "The schedule is set to be done in February so we will see how that goes. After that, I'm looking for a unification bout. I want one champion, one face and one name and he go by the name of Deontay Wilder.
"They have to be perfect for 12 rounds, I only have to be perfect for two seconds"
But the World was blown away by the savagery of the KO, after Wilder looked to be out of sorts throughout the fight.
Even fellow boxers were blown away.
Two-time Welterweight champion Shawn Porter said Wilder had something special that hadn't been seen in the heavyweight division.
"We haven't seen power like that in the heavyweight division since Mike Tyson," he said.
Actually, it's never been seen before.
Wilder's win takes him to a 42-0-1 record with a stunning 41 KOs — a 97 per cent knockout ratio, the highest in history.
But other boxers were also floored as hard as Ortiz by the knockout.
ROUND BY ROUND
Round 1: A slow start to round one but Wilder has already opened Ortiz after a head clash but Ortiz got the best of the limited action. 10-9 Ortiz.
Round 2: Another round of feeling each other out but Ortiz had a couple of little flurries with Wilder offering little. 20-18 Ortiz
Round 3: Wilder seems to be in a bit of trouble here. The bronze bomber has been letting the fight come to him with Ortiz getting in the better of the jobs. 30-27 Ortiz
Round 4: Wilder is getting cranky, trying to wake himself up by beating his chest but it did little as another round went to Ortiz. 40-36 Ortiz.
Round 5: Wilder is looking for the knockout punch rather than going toe-to-toe but it seems to be playing into the hands or the Cuban. We have it five rounds for Ortiz. But Wilder has a 95 per cent KO rate, the highest in history — 50-45 Ortiz
Round 6: The perfect start from Ortiz with Wilder looking for the KO, quickly becoming his only hope. 60-44 Ortiz at the halfway mark
Round 7: Ortiz seems to getting fatigued as Wilder starts to accelerate. But with three seconds left in the seventh, Wilder knocked Ortiz out, the referee waves it off and Wilder wins, retaining his World title.