Unbeaten Deontay Wilder landed a devastating right hand to knock out Luis Ortiz in the seventh round and retain his World Boxing Council heavyweight title.
The 34-year-old Wilder remains on course to achieve his goal of unifying all four heavyweight belts despite being largely outboxed by Ortiz before the explosive one-punch finish at the MGM Grand Hotel in Las Vegas late Saturday night.
"When I see the right shot, it is baby good night," Wilder said.
Unbeaten in 43 fights, Wilder showed why he is widely regarded as the most destructive puncher in the resurgent heavyweight division.
The "Bronze Bomber" recorded his 10th straight title defence to equal Muhammad Ali who achieved the feat between 1974 and 1978. Only four heavyweights in the history of boxing have made more than 10 consecutive title defences.
Wilder waited patiently for his big moment and when it came, with just nine seconds left in the round, it was stunning.
He followed a pawing jab with a crushing straight right that sent Ortiz's head snapping back and his body crashing into the ropes before landing on the canvas.
"That was a punch intended to hurt for sure," said the American. "I got him at the right angle, my feet were planted perfectly and I felt the torque."
Ortiz tried to get up but he clearly could not continue. The fight was officially stopped at 2:51 of the seventh.
- Unification goal -
It was a repeat of their 2018 fight where Wilder had battled adversity to deliver a 10th-round stoppage.
Wilder's win now sets up another money-spinning rematch with Tyson Fury scheduled for February.
If he comes through that a unification showdown against the winner of next month's rematch between Anthony Joshua and Andy Ruiz in Saudi Arabia for the other three major heavyweight belts could follow.
The fights with Fury, and Ruiz or Joshua, would generate millions for Wilder.
The last two years in heavyweight boxing have provided plenty of rousing match-ups and renewed enthusiasm in contrast to the previous 15 years or so which were dominated by the Klitschko brothers.
"I am looking for a unification bout," Wilder said. "I want one champion, one face, one name that goes by Deontay Wilder.
"The heavyweight division is too small to have so many belts lingering around. It should be just be one champion and I think I am the perfect man for that job."
The 40-year-old Ortiz, who was coming off three straight victories, was trying to become the first Cuban to win the world heavyweight title.
- 'It was a war' -
"This is boxing. I told everyone it wasn't going to go 12 rounds," said Ortiz.
Ortiz won most of the early rounds. He was the aggressor from the opening bell as he tagged Wilder with a left hook to the face in the opening round.
Ortiz also suffered a cut to his right temple area in the opening round due to an accidental clash of heads. But there was little blood flow and his corner did a good job of containing it as the rounds continued.
Both fighters were waiting for an opening in the second round and by the third Ortiz was building up points because he was the busier of the two.
Ortiz landed a big overhand shot in the fourth which excited the crowd and pumped up Wilder, who pounded his chest and yelled bring it on.
Ortiz's plan to was to fight inside and pay attention to defence while Wilder was constantly looking for the knockout shot and hoping Ortiz would eventually tire himself out.
That transpired in the seventh as Ortiz walked straight into a punch that appeared to come out of nowhere, sending the Cuban into dreamland.
"I don't care about losing rounds because it is a 12-round fight," said Wilder. "I wanted to time my punches and do the right thing.
"I had to strategically move Ortiz. I had to time myself and calculate my punches. It was a war."
Ortiz wasn't so sure it should have been stopped even though he barely managed to wobble to his feet after the knockdown.
"I was clear-headed. When the count was at seven I was still trying to get up. Maybe the count was quicker than I thought," he said.