Floyd Mayweather equalled former heavyweight great Rocky Marciano's 49-0 record with a unanimous decision victory over Andre Berto before promptly announcing his retirement.
Mayweather, who repeated his insistence in the build-up that this bout would be his last, was the heavy betting favourite and unsurprisingly dominated his overmatched foe to retain his WBC and WBA welterweight titles.
Scores of 120-108, 118-110 and 117-111 took the five-weight world champion, almost universally regarded as the pound-for-pound best in the sport, to his 49th consecutive victory in the professional ranks.
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Yet the 38-year-old seems to have no desire to reach a half-century as he said in his in-ring interview: "My career is over, that's official.
"You've got to know when to hang it up. I'm close to 40 now. There's nothing left to prove in the sport of boxing. Now I just want to spend time with my family"
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Many pundits are sceptical of Mayweather, who has announced his intention to walk away from the sport in the past only to make a comeback, most notably returning to face Juan Manuel Marquez in July 2009 21 months after 'retiring' following his knockout of Ricky Hatton.
Yet the veteran does not have any contractual obligations to fulfil after completing his highly lucrative six-fight deal with Showtime, an arrangement which saw him become the highest earning sportsman in the world, according to Forbes.
If this is to be the last bout of a glittering 19-year professional career, he bowed out in style against a game challenger, albeit one who has attracted plenty of criticism in the build-up.
With three defeats in his last six fights, Berto was largely viewed as an unworthy foe for Mayweather, with British pair Amir Khan and Kell Brook and rising American Keith Thurman seen as more attractive alternatives.
Berto tried his best but, as anticipated, he was not on the same level as Mayweather, who outpointed welterweight foe Manny Pacquiao in his last bout in May in what was billed as the 'Fight of the Century'.
A sharp left hook from the champion punctuated a slow first round although, ominously for Berto, Mayweather was immediately finding his range with the jab.
He seemed content to allow Berto the centre of the ring in the second, but the underdog, as high as 18/1 to win with some bookmakers, was struggling to land anything clean.
Mayweather was on the canvas in the third after a slip but he quickly regained control, and in the fourth a big right hand wobbled Berto, who managed to survive the round before unsuccessfully attempting to drag his opponent into the trenches in the fifth.
Berto landed his best punch of the fight in the next round with a counter left but Mayweather responded with a rapid-fire flurry on the bell.
Another chopping left from Berto once again seemed to bring Mayweather out of his reverie in the seventh, with the Haitian-American's trainer Virgil Hunter urging his charge to "walk through" the pound-for-pound king before the start of the eighth round.
Berto responded by trying to get to work on the inside but Mayweather characteristically showed excellent defensive reflexes before firing off a few jabs.
The pair were involved in a verbal exchange as the ninth round came to an end before then going toe-to-toe, with Mayweather coming out on top, while the pair were warned by referee in Kenny Bayliss in the 10th for their trash-talking.
Maywather's punch output was low but his accuracy was high and he started to showboat towards the end of the 11th with an 'Ali Shuffle' to an equal amount of cheers and boos from the MGM crowd.
He closed strongly with a right uppercut rocking Berto in the final minute but could not force his first stoppage victory since beating Victor Ortiz in 2011.
But he sank to his knees at the conclusion of the bout, knowing he had done more than enough to bow out of the sport with one more victory on his ledger.