Saul 'Canelo' Alvarez produced a near-flawless display to unpick Callum Smith and take the British fighter's WBA world super-middleweight title.
The Mexican, 30, shone in Texas as he all but froze Smith out over 12 rounds with calculated pressure, spiteful punching and evasive defensive work.
Smith, 30, struggled to land anything heavy and was told by his corner he had "one more round" after a torrid ninth.
He admirably fought on but lost 119-109 119-109 117-111 on the judges' cards.
Alvarez - who has only one defeat on his record from 57 fights - also picked up the vacant WBC world super-middleweight title, meaning he holds two of the four significant belts at 168lbs.
"I'm devastated. I came here to win," Smith told DAZN at the Alamodome in San Antonio. "No excuses, he was very good.
"It could have been a better version of me. He is smart and he is clever. He closes ground, sets traps and before you know it he's closed the ground up. I maybe let him close the ground up too easily."
'A bad beating'
Smith's seven-inch height advantage had formed much of the foundation for those suggesting he could defy his underdog status.
But Alvarez refused to take a step back at any point. He shut down space patiently, remained compact, showed head movement and ultimately made himself difficult to hit.
When he was close enough, he jabbed smartly and loaded up with his trademark shots to the body.
At the end of the fifth, Smith's three older fighting brothers shouted "better" from ringside as he began to throw more but in the seventh, Alvarez - the youngest of seven fighting brothers - landed hard body shots on the counter and a fine uppercut.
A hard right hand sent Smith slumping into the ropes in the ninth and, with his nose bloodied, he replied to trainer Joe Gallagher that he was "fine" after it was made clear he would only get one more round.
Ominously, four-weight world champion Alvarez explained he knew he could take Smith's power "from the first round" and it was later revealed the Liverpool fighter may have torn a bicep early in the contest.
Alvarez simply presented a puzzle his opponent never looked like solving. By the 10th round, US broadcasters were calling the fight "a bad beating".
"This is one of the best nights I have had," said Alvarez, who added he would consider a third fight with Gennady Golovkin, who beat Kamil Szeremeta 24 hours earlier.
"One of the greatest nights. I will go for more. I want all the belts, it doesn't matter who has them. I don't run from anybody. I have fought against the best. I have shown the world I fight the best."
A hunger clearly remains
Alvarez has now reeled off five wins since his six-month ban for failing drugs tests in 2018. His sole loss in 15 years was against Floyd Mayweather in 2013 but his current momentum and this well-rounded display underline why he is the sport's best-paid star.
A restricted crowd of about 12,000 may have impacted on his overall earnings in his first bout in 13 months but his quality is undeniable, his rivals look a class below, and crucially his hunger appears undiminished.
The iconic middleweight Marvin Hagler once said: "It's tough to get out of bed to do roadwork at 5am when you've been sleeping in silk pyjamas."
The sight of Alvarez walking round the fight hotel's bubble in designer pyjamas this week prompted questions as to how much more he could give.
His status, earning power and lifestyle are far removed from the life he knew on his family's farm as a child but there can be no doubt his grit and desire remain, and future rivals will need to find something special to stop him.
Smith can be proud of his own journey to face a man he once dreamed of fighting. Alvarez, though, was simply too good.
Class, tears and call-outs - what they said...
Cutting a dejected figure in his corner, Smith said he would take time out and consider a move up to the 175lbs light-heavyweight division.
His sentiment led BBC 5 Live commentator Mike Costello to wonder if he was considering calling time on his career at the age of 30.
Britain's Billy Joe Saunders - who holds the WBO belt at super-middleweight - quickly tweeted to call on Alvarez to "get it on" in 2021 but for the most part, the boxing world was simply left praising the sport's biggest star.
Promoter Eddie Hearn confirmed Smith damaged his arm early on in his San Antonio defeat and revealed the fighter was "in tears" in the changing room.
"It was a masterclass from Canelo," Hearn told 5 Live.
"I just left Callum's changing room and everyone is talking about Alvarez. He's just so good. Callum never stopped throwing but he came up against the best fighter on the planet."
Former world champion George Groves told BBC Radio 5 Live: "Canelo bullied Smith, marched him down and used his punch power to control the entire fight."
And BBC Radio 5 Live boxing analyst Steve Bunce added: "That's what happens when you fight Canelo. You discover things about yourself you didn't know and things about him you didn't recognise before you got in the ring.
"Smith has been broken. Canelo took away his height, reach and confidence. That is class."
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