Gennady Golovkin has spent the last several years looking for a challenge. He'll have to keep looking.

In a dominant effort, Golovkin scored an eighth-round TKO over IBF middleweight champion David Lemieux in a title unification bout at Madison Square Garden Saturday night.

Referee Steve Willis appeared to be looking for a reason to stop the fight as early as the seventh round. A wicked Golovkin right hand that sent Lemieux reeling was finally enough for Willis. Golovkin had won all seven rounds on the official scorecards.

"I told you this was a very important fight," Golovkin said. "Dave is a very good fighter. A strong fighter. I can box him, too. I'm a boxer, too. My goal is all the belts in the middleweight division."

Golovkin, of Kazakhstan, adds the IBF belt to his own WBC-WBA titles. He improves to 34-0 with 31 knockouts, including 21 straight stoppages.

Lemieux, from Montreal, falls to 34-3.

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Golovkin has all but cleaned out the middleweight division, having held some form of the middleweight title since 2010.

The next challenge on the horizon for Golovkin should be the winner of the Miguel Cotto-Canelo Alvarez showdown Nov. 21.

"I'm a boxer. Not a businessman," Golovkin said when asked about the Cotto-Canelo fight. "I want all the belts. I want to bring my fans big events. Both are great champions. I want who wins."

The Garden was sold out for this fight by Thursday, with an announced attendance of 20,548. The last middleweight unification bout came in September 2001, when Bernard Hopkins stopped Felix Trinidad in the 12th round to become undisputed champion.

Hopkins, who promotes Lemieux with Oscar de la Hoya's Golden Boy Promotions, said that Lemieux would have to be nearly perfect to win. It was Golovkin who was perfect.

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Golovkin, 33, controlled the early rounds with a hard left jab. By the close of the second, he was following the jab with right hands and Lemieux had no real answer for it. Lemieux, 26, tried to crouch and barrel his way into punching range. Any progress he made usually was met with a Golovkin jab or right counter.

Lemieux got the first real taste of Golovkin's power in the fourth round, when a wide left hook buckled his knees. He waved Golovkin in for more, who obliged him with several blistering right hands. Lemieux then pressed his attack in the fifth, landing a hard left-right combo, but moments later, a vicious left hook to the body dropped him to one knee in the center of the ring.

Golovkin continued his clinical demolition of Lemieux until Willis stopped the fight.

In the semifinal, Ramon Gonzalez of Nicaragua retained his WBC flyweight title with a ninth-round stoppage of Brian Viloria.

Gonzalez (44-0 with 38 knockouts) is considered one of the best pound-for-pound fighters in the world. He methodically wore down Viloria, a former U.S. Olympian from Hawaii.

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Gonzalez pressured Viloria for much of the bout with a steady stream of combinations. Viloria, a two-division world champion, fell to 36-5.

In the opening pay-per-view bout, Tureano Johnson of the Bahamas scored a unanimous 12-round decision over Eamonn O'Kane of Ireland in an IBF middleweight title elimination bout.

In a bout for the WBA interim heavyweight title, Luis Ortiz, from Miami, knocked out Matias Vidondo of Argentina at 17 seconds of the third round.