The Krusher is back.

Sergey Kovalev, long one of the most feared punchers in boxing, said he reloaded inside and outside the ring after back-to-back losses to Andre Ward. He changed his life, he said, to become more serious about the sport he loves.

And his opponent, Vyacheslav Shabranskyy, learned just how serious in a hurry Saturday night as the overmatched Ukrainian was knocked down three times in the first two rounds before referee Harvey Dock stopped it at 2:36 of the second at the Theater at Madison Square Garden.

After losing his three titles to Ward, Kovalev used his powerful right hand to get one of them back. And it took him less than six minutes to do it. The WBO belt, which was vacated after Ward retired in September, is back in the hands of Kovalev, who improved to 31-2-1 (27 KOs). Shabranskyy fell to 19-2 (16 KOs).

For Kovalev, it was simply target practice from the opening bell, as Shabranskyy stood in front of the 34-year-old Russian and paid dearly for it. Kovalev landed 50 punches to only 16 for Shabranskyy.

“I did it. I reloaded my brain, mentally, and conditioned my body,” Kovalev said. “I’m back. It’s my goal to be the best in this division. I don’t think in the last fight (his first career stoppage vs. Ward) I was stopped. It was an illegal decision by the referee. But I’m ready to fight for all the titles, unified titles. ... I love boxing and I’m looking forward to making great fights.”

The division is full of stars, old and new champions, two of whom came from Russia: Dmitry Bivol, 26, holds the WBA belt, and was at ringside Saturday. Artur Beterbiev, 32, now living in Canada, holds the IBF belt. And 40-year-old Canadian Adonis Stevenson has held the WBC belt since 2013 but has avoided a fight against Kovalev.

“Krusher” likes the way the division shapes up at the moment.

“The belts have different owners, and that makes the boxing very much interesting,” he said. “We can make good fights for the boxing fans and also for boxing history. I just want to find out who is the best in the light heavyweight division in the future.”

Kovalev called all the other titleholders out afterwards.

“Chicken (Stevenson) is on my list, too, but I’m ready for any champion, like Bivol, and Beterbiev because this is very good for boxing. Let’s do it. I’m ready.”

On the televised undercard, Cuban slugger Sullivan Barrera scored a unanimous decision against a very game Felix Valera in a 10-round light-heavyweight title eliminator. Barrera will fight Bivol, who scouted his next opponent from ringside. Barrera improved to 21-1 (14 KOs), while Valera, from the Dominican Republic, who had three points taken for low blows, fell to 15-2 with 13 KOs.