One of the most controversial and best fights of 2021 finally happened on Saturday when Jermell Charlo and Brian Castano locked horns to determine an undisputed super welterweight champion. 

Charlo made sure there was not another disputed decision as he dropped Castano twice to win by tenth-round knockout to become the undisputed super-welterweight champion from Dignity Health Sports Park in Carson, Calif. DAZN had the fight scored 87-84 for Charlo going into the tenth round. Charlo and Castano continued their 2021 "Fight of the Year" candidate by having a back-and-forth war through the first half of the fight, with neither guy taking a back seat. So who would make the adjustment in the second half to walk out of California the champion?

It was Charlo (35-1-1, 19 KOs). The 31-year-old started sitting down on his shots, throwing power shots that were taking their toll Castano, and setting everything up with the jab. Castano had no answer as to what to do, and his activity started to slow as the fight entered the championship rounds. 

In the tenth round, Charlo and Castano were in close range when the former landed a short left hook. It appeared Castano ate the blow well, but it was a delayed reaction and the native of Argentina went to the canvas. Castano made it back to his feet, but he was shaky and all over the place. The fight should have been stopped at that point, but the referee let it continue. Charlo smelled blood in the water and pounced like a shark.

A right hand sent Castano back to the ropes. Charlo closed the show with a left uppercut which lifted Castano off his feet. The next and final blow was a left to the body that sent Castano packing and we have the first four-belt champion at 154 pounds. 

Charlo joins Terence Crawford, Josh Taylor, Bernard Hopkins, Jermain Taylor, Canelo Alvarez, and Oleksandr Usyk as the only male fighters to become undisputed champions in the four-belt era.

Here is what happened at Jermell Charlo vs. Brian Castano 2.