Deontay Wilder paved the way for a megafight with Anthony Joshua with a brutal stoppage of Luis Ortiz in New York.
But the Bronze Bomber did not have it all his own way in a rollercoaster clash against the previously undefeated Cuban.
Wilder, who had ended all but one of his previous 39 wins inside the distance, seemed to be sailing to another knockout win when he dropped Ortiz late in the fifth round.
But the challenger rallied during a huge seventh round and appeared to have his American opponent out on his feet when the bell went.
The tense clash then swung wildly once more in a mad 10th round which had Ortiz down and out with just 55 seconds left until the bell.
The final blow was a crippling uppercut which sent Ortiz down to his knees, giving referee David Fields no choice but to wave it off instantly.
Now the WBC king, who has answered any remaining questions about the quality of his chin, can look forward to a potential fight for the ages against Joshua later this year.
The WBA and IBF champ from Watford has the chance to add the WBO crown to his collection when he faces undefeated New Zealander Joseph Parker in Cardiff later this month.
Now it feels like only a matter of time before Wilder and Joshua tangle in a transatlantic tussle which could smash all previous revenue records.
The 32-year-old said: “I always said I want to unify all the titles. My goal is to unify.
“I am the most dangerous in the world, the baddest man on the planet. I proved that tonight.
“Soon there will be one champion, one face, one name – that will be Deontay Wilder.
“It’s not about how big your muscles are – it’s about the heart.”