LAS VEGAS — Andre Ward vowed he would leave no doubt this time around and he didn’t, stopping Sergey Kovalev in the eighth round Saturday night to win their light heavyweight title rematch.

The undefeated Ward turned the fight around with a big right hand that wobbled Kovalev, then swarmed all over him. Kovalev was in the neutral corner and Ward was landing shots to the body when Kovalev sat on the ring rope and referee Tony Weeks signaled an end to the bout at 2:29 of the eighth.

“I knew this time it was going to be different,” Ward said.

The fight had been close until Ward (32-0) turned it around with the right hand, with Kovalev (30-2-1) winning the early rounds before Ward began making adjustments and Kovalev began tiring. Both fighters complained of dirty tactics and Weeks spent a lot of his time breaking up clinches.

Ward won the first fight in November, coming back from a second round knockdown to get a controversial decision. The rematch seemed just as close until Ward landed the right hand that caused Kovalev’s legs to wobble.

“He’s a great fighter,” Ward said. “You’ve got to raise your game to the next level and thankfully that’s what we did tonight.”

Kovalev complained that Ward hit him with two low blows in the final exchange, forcing him to sit on the first rope.

“Why stop the fight?” he said. “I could have continued to fight.”

The fight was rough and tumble from the beginning, much like when the two met the first time when both were unbeaten. But while Kovalev was supposed to be the puncher it was a big right hand by Ward that landed midway through the eighth.

“I could tell he was reacting to my body shots and I knew I had him then,” Ward said. “I knew he was hurt.”

Ward was up by a point on two scorecards and down three points on the third going into the eighth. But Kovalev was fading, just as he had in the first fight, and he picked up the pace. Kovalev was credited with throwing 407 punches to 238 for Ward, and outlanding him 95-80.

There was genuine dislike between the two fighters, born largely out of their first fight. Neither made any effort to touch gloves when given their final instructions, and once the bell rang, they both went after each other.

The fight itself played out early somewhat like the first one, with Kovalev starting out aggressively and Ward trying to find his rhythm. Weeks, meanwhile, was working hard to keep control as the two fighters clinched and hit each other behind the head, with Ward landing a low blow in the second round that doubled Kovalev over and caused Weeks to pause the bout.