Amanda Nunes won in spectacular fashion. Jon Jones barely hung on.
Both champions still emerged from UFC 239 with their belts around their waists.
Nunes stopped Holly Holm late in the first round to defend her bantamweight title, and Jones squeaked out a split-decision victory over Thiago Santos to defend his light heavyweight title Saturday night.
A two-division champion on a nine-fight winning streak, Nunes (18-4) remained the pound-for-pound ruler of her sport with her usual devastating flair. After she floored Holm (12-5) with a perfectly timed kick to the head, she mercilessly finished Holm with punches on the ground with 50 seconds left in the first round.
"I told my coaches I wanted to knock her out the same way she knocks people out," Nunes said of her opponent, an accomplished kickboxer. "I did it tonight. She was the only former champion I didn't beat yet. Now I beat her, and I'm very happy."
Jones (25-1) had much more trouble with Santos (21-7), who nearly scrapped his way to victory despite injuring his left knee early in the fight. Jones fought cautiously and earned a 48-47 decision on two of the three judges' scorecards.
"He implemented a game plan I think a lot of people have wanted to for a very long time," Jones said. "He did a good job. He exploited a hole in my game that won't be there next time."
Until Jones' tactical victory, UFC 239 was all about violence.
Jorge Masvidal knocked out previously unbeaten Ben Askren with a sensational flying knee just 5 seconds into their bout on a card peppered with jaw-dropping finishes until Jones' decision.
Jan Blachowicz also knocked out Luke Rockhold with a devastating left hand in the second round of ex-champ Rockhold's light heavyweight debut.
Nunes took a few minutes to find her groove against Holm, who famously knocked out Ronda Rousey with a head kick nearly four years ago. When Nunes felt comfortable, she unleashed a sophisticated array of strikes and eventually caught Holm with a kick that sent her straight to the canvas.
Nunes completed the knockout with punches, sending Holm to her fifth loss in seven fights.
After her fourth successful bantamweight defense, Nunes said she wants to defend the 145-pound belt next. UFC President Dana White is trying to book a rematch with long-reigning featherweight champion Cris "Cyborg" Justino, who lasted just 51 seconds against Nunes in December.
"This woman is tough, man," White said of Nunes. "She's unbelievable. Pound for pound, one of the greatest of all time. But there will be somebody next."
Jones was a significant favorite against Santos, a longtime middleweight who moved up in weight last year. But Santos' power and energy caused problems for Jones from the opening minutes, forcing the champion to be cautious and to use his superior length.
"We all knew Thiago's best chance was to knock me out," Jones said. "I played it smart and brought home this gold for my family and team. He was technically a lot more sound than I thought. Thiago Santos is a black belt in Muay Thai. I'm proud of myself, because I stood with a guy who's been kickboxing way longer than me."
Santos landed several significant strikes in the first round, but Jones briefly floored the challenger with a big kick in the second.
"I thought I hit him more and out-pointed him, but with my knee like that, it was all I could do," Santos said. "I knew it was a very close fight. In the condition I was in, I thought I fought a good fight."
Jones found his rhythm midway through the fight, using his size to keep Santos away. Santos also hurt his knee along the way, although he kept striking even while he struggled for balance.
"I felt like I was winning, so there was no need to take him down," Jones said. "We were playing a very high level game of chess in there."
Masvidal (34-13) played a less complicated game to get his star-making finish.
Masvidal authored one of the most dramatic knockouts in UFC history when he destroyed Askren (19-1), a high-level wrestler in his second UFC fight after a prosperous career in other promotions. Masvidal and Askren had an intense personal rivalry heading into the fight, exchanging voluminous trash talk rooted in years of mutual dislike.
After listening to the opening bell while touching his own fence, Masvidal took three running steps out of his corner and sailed directly into the face of Askren, who had ducked for a wrestling takedown. The knee landed flush, and Askren was unconscious.
Masvidal then landed two punches to the defenseless Askren's head before the referee could stop the bout after only 5 seconds. Masvidal then celebrated in the cage while Askren struggled for several minutes to gain coherence.
"I'm glad I got to end that dude, man," Masvidal said. "He's so predictable. He's a scrub. ... It was like, 'Come and eat.' He probably thought he was going to get a three-piece (dinner). Nah, you're getting a whole MGM Grand buffet to the face, man."