NEW YORK (AP) When Deontay Wilder finally took off the gold mask he wore into the ring, he displayed a fierce scowl.
That look never disappeared from his face as he knocked out the only man who'd ever gone the distance with him.
Wilder sent Bermane Stiverne to the canvas three times in the opening round to defend his WBC heavyweight title Saturday night at Barclays Center.
''So much frustration, it just seemed like my career, it's been crazy . so many guys using PEDs,'' Wilder said. ''I just want to prove that I am the best. I know I am the best, but I wanna prove I am the best.''
There wasn't much question of that in the Showtime card that ended in spectacular fashion.
The 32-year-old Wilder jabbed through much of the first round while Stiverne, who hadn't fought in two years, moved slowly and cautiously around the ring. Suddenly, Wilder lashed out with a huge right that felled Stiverne (25-3-1).
Already, Wilder was celebrating, but Stiverne got up. Unwisely, it turned out, because another big right as part of a flurry of punches sent the 38-year-old challenger back down.
At that point, Wilder climbed atop the ropes in a neutral corner, shouting at Stiverne's trainer to end things.
When they didn't, another right and then a mammoth left hook sent down the challenger for the final time with his ''Alabama Slammer.''
''One champion, one face, one name, he goes by Deontay Wilder,'' the WBC champ said.
Wilder won the belt from Stiverne in 2015 in a 12-round decision. He repeatedly insisted Stiverne would go down and out early in this one.
Wilder kept his word.
He is 39-0 with 38 knockouts.
Wilder now can set his sights on something he has been promising throughout 2017: unifying the heavyweight belts. He wants England's Anthony Joshua, the WBA/IBF champ, sometime next year, and was busy issuing challenges after disposing of Stiverne.
''I've been waiting on that fight for a long time now,'' he said. ''I declare war upon you. Do you accept my challenge?
''I know I'm the champion, I know I'm the best. Are you up for the test?''
This was Wilder's sixth defense, and his most ferocious. Stiverne, who last fought on Nov. 14, 2015, outpointing Derric Rossy, never had a chance. He was a substitute for Jose Ortiz, who failed a drug test.
Stiverne did not land a punch and never should have bothered showing up.
Earlier, Sergey Lipinets won a unanimous decision over Akihiro Kondo for the vacant IBF junior welterweight title, a decision that was lustily booed by the crowd of 10,924 at Barclays Center.
In a bout featuring lots of action but lots of missed punches, the 28-year-old Lipinets of Kazakhstan won despite dealing with a cut on the forehead that bled for the final six rounds. He won 118-111 on one judge's card and 117-111 on two others even though Kondo, fighting outside of his native Japan for the first time, carried much of the action in the second half of the bout.
The AP scored it 115-113 for Lipinets, who is 13-0. Kondo fell to 29-7-1, losing for the first time in nine fights.
''The head butt really impaired my vision and it led to me walking into some stupid shots,'' Lipinets said.
Shawn Porter pummeled Adrian Granados for most of 12 rounds in a lopsided fight. There were more clinches in the first round of that fight than in the entire Lipinets-Kondo matchup.
Porter is in line for another welterweight championship opportunity; he held the IBF crown in 2013-14. He improved to 28-2-1 in a bout that had little style, but plenty of action. The judges all had it 117-111 for Porter.
''He gave me a little trouble here and there,'' said Porter, who wants a rematch with WBA champ Keith Thurman, who beat him at Barclays Center last year. ''I hurt my left hand in the sixth round, but I kept using it. I had to use my jab. It took a toll on me and by the 10th round I just couldn't throw it anymore.''
Granados is now 18-6-2.
In what was billed a heavyweight eliminator, Dominic Breazeale (19-1, 17 KOs) stopped Eric Molina after eight rounds. Molina, exhausted after taking a battering in the eighth, had his arms hanging over the ropes when the round ended. A ringside doctor then stopped it.
Molina (26-5) previously has lost to both Wilder and to WBA-IBF champion Anthony Joshua. Breazeale also has lost to Joshua.
""Deontay is who I want to face,"" Breazeale said.