Nearly four years after De Los Santos stopped Valenzuela inside three rounds, it was Valenzuela who exacted revenge by detonating De Los Santos with a dynamite second-round knockout to headline Zuffa Boxing 08 at The Cosmopolitan in Las Vegas.

Valenzuela (16-3, 10 KOs) rocked De Los Santos (17-3, 15 KOs) in the opening round of their lightweight bout with a pair of vicious overhand left hooks and wasted little time in the second to lay his nemesis to waste with a violent counter right hook that knocked De Los Santos down and out at the 2:05 mark of the round.

Valenzuela hit De Los Santos with a punch after he was down, but referee Thomas Taylor ruled that it didn't factor into the devastating sequence that preceded it. If revenge is a dish best served cold, Valenzuela did so by icing De Los Santos in sensational fashion. De Los Santos and Valenzuela traded knockdowns in a three-round firefight nearly four years ago, and it was the unknown De Los Santos who stepped in on one a day’s notice to dominate “Rayo” in a three-round war to hand the then-rising prospect his first career loss.

De Los Santos was dropped once, and Valenzuela twice before the fight ended with Valenzuela still on his feet.

But just like in the first fight, De Los Santos’ recklessness reared its ugly head again as he overcommitted several times in the sequel, which allowed Valenzuela to convincingly get his vengeance.

“I see he didn't want to engage in the second round; he was hurt after the first round,” Valenzuela said after the fight, “So I knew I had to get him and jump on him before he recovered.

“I was a boy when we first fought. I grew up, man. I matured a lot. I evolved. This is a good example for everybody out there that you can get better.”

With only one round under his belt since fighting to a lackluster decision loss against then-WBC lightweight champion Shakur Stevenson in November 2023, De Los Santos appeared unfit for the occasion compared to Valenzuela, who’d fought five times in the same span and even scored a 140-pound WBA title in between.

The 27-year-old Valenzuela is now 4-3 in his last seven fights, including the loss to De Los Santos in September 2022.

After dropping a unanimous decision defeat to Chris Colbert right after the De Los Santos fight, Valenzuela righted the controversial scorecards by stopping Colbert in an immediate rematch. Valenzuela then beat Isaac Cruz for the title he held before dropping it to Gary Antuanne Russell in March of last year.

Valenzuela made his Zuffa Boxing debut in February with a 10-round unanimous decision win against Diego Torres.

He also called out The Ring and 140-pound champion Stevenson while basking in his latest victory.

“It's one of the best feelings in the world,” Valenzuela said. “I just knew what kind of fighter I was. I knew I was better and more complete [than De Los Santos]. I was probably at 30 percent of my abilities in the first fight. I know at 100 percent, I'm hard to beat.

“You can lose, come back and evolve to become a better fighter and human being, and that's what I did.