Artur Beterbiev ruthlessly demolished Joe Smith Jr inside two rounds at Madison Square Garden to add the WBO light-heavyweight title to his IBF and WBC belts.
Beterbiev dropped his opponent three times before referee Harvey Dock called a halt to the one-sided contest and confirmed victory for the hard-hitting Russian-born Canadian.
Only Dmitry Bivol, who holds the WBA version of the light-heavyweight title, now stands in the way of a clean sweep of the division for the undefeated 37-year-old.
“I wanted to be a good boxer today,” said Beterbiev, who extended his professional record to 18 knockouts from 18. “That’s why I was a little bit better than I was in the past.
“Joe is a little bit open and it was more easy for me to get him. It was two fighters who both have a good punch and both were trying to get there first.
Joe Smith Jr was unable to withstand Beterbiev’s power
“This time, I got lucky and got him first. Unification fights are more interesting, more motivating – I want to be undisputed.”
Smith, who went into the ring with a 28-3 record, was stopped for only the second time in his career as his defence proved inadequate to repel Beterbiev’s power.
A barrage of heavy right hands found their mark in the opening round, with one sending Smith onto one knee just before the bell.
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Smith sprang back up after taking a similar shot early in the second, but he was then sent sprawling into the ropes by a left soon afterwards.
Left and right uppercuts followed in the wake of the third knockdown and when Smith was wobbled again by another right that landed on the back of his head, the referee stepped in with 41 seconds remaining in the round.