Sebastian Fundora defeated Australia's Tim Tszyu by technical knockout to retain his World Boxing Council super-welterweight crown in Las Vegas on Saturday.
A bruising, action-packed scrap at the MGM Grand Garden Arena ended when a bloodied Tszyu failed to come out for the eighth round.
Fundora – who had beaten Tszyu in their first meeting last year – once again used his towering 6ft 6in (1.98m) frame and huge reach advantage to dominate the short, stocky Australian.
Tszyu was quickly in trouble, knocked down by Fundora in the first round by a crisp left hand, and finished the second round with a nasty cut over his right eye.
Although Tszyu battled bravely, jolting Fundora with some shuddering right-hands in the middle rounds, the American continued to land damaging punches.
The end came after the seventh, when a weary Tszyu declined to come out for the next round.
"I gave it everything but I just couldn't do it," Tszyu said afterwards. "Victory belongs to Sebastian Fundora – he's the best 154-pounder on the planet right now.
"He was the better man. He's very hard to land, and he's tall ... I felt like I was shadow boxing with myself at times. It is what it is."
Fundora, 27, who improved to 23-1-1, with 15 knockouts, said he had been determined to exploit his advantages of height and reach.
"I felt like obviously I'm the bigger guy, and everyone's calling me a bully – so you know what, let's start bullying these guys," Fundora said.