An emotional Francis Ngannou marked his return to mixed martial arts with a first-round stoppage of Renan Ferreira at the PFL Super Fights event in Riyadh, Saudi Arabia.
Cameroon's Ngannou knocked out Ferreira with some brutal ground strikes in his first MMA contest in nearly three years.
The 38-year-old shed tears as he dedicated the victory to his late 15-month-old son Kobe, who passed away earlier this year.
"I can't think about anything [other] than my son Kobe. I only took this fight because of him," said Ngannou.
"I went to fight for him. I hope they can remember his name because without Kobe, we wouldn't be here tonight. I wouldn't have fought."
Since leaving the UFC as its heavyweight champion 22 months ago, Ngannou has become one of the world's biggest combat sports stars following blockbuster boxing bouts against Tyson Fury and Anthony Joshua.
But he has been adamant in the build-up to this encounter that he "never left MMA", and always planned to fight again in the cage.
Ngannou considered retirement earlier this year, but said he had chosen to fight on as a way of "honouring him".
Making his PFL debut, the organisation took advantage of the money their biggest star now generates by building the card around Ngannou and creating commemorative 'Super Fight belts'.
Announced as the "one true heavyweight MMA champion" in reference to his being stripped of his UFC title after leaving the promotion early last year, Ngannou opened the contest billed as 'the Battle of the Giants' with a leg kick, wobbling Ferreira.
Ferreira, the PFL's 2023 global league heavyweight champion, responded with a leg kick of his own, but would soon find himself on the back foot as Ngannou secured a takedown.
After defending a triangle choke attempt, Ngannou took control, posturing up and launching a series of ground strikes down on a helpless Ferreira.
With the Brazilian not defending himself, the referee stopped the contest as an emotional Ngannou crouched against the cage, gathering his thoughts in victory.
"I knew I didn't miss a step. I wasn't worried about it because as soon as I walked in the gym I knew everything was still there," said Ngannou.
"It was just me being able to manage my emotions. Deal with life separately, not mix things up. That's what I have been working on.
"I think my next move in combat sports all depends on me, how I feel. I always think I have a lot to give and I keep thinking that way."
The card was typical of recent big sporting events to take place in Saudi Arabia, with a glamorous opening ceremony.
National flags of each fighter competing were paraded to the cage, ending with the Saudi Arabian national anthem, as global stars such as Portuguese footballer Cristiano Ronaldo watched.
The country continues to face criticisms, however, for using sport to divert attention away from its poor human rights record - a process dubbed 'sportswashing'.
In the co-main event, Brazil's Cris Cyborg beat compatriot Larissa Pacheco by unanimous decision in a gruelling back-and-forth contest.
In a fight where momentum changed multiple times, Cyborg, 39, was the more aggressive as she cemented her legacy as one of the best female MMA fighters in history.
The bout was billed as a champion versus champion contest, with Cyborg the reigning Bellator featherweight title holder and Pacheco winning the 2023 PFL featherweight global league.
Cyborg referred pre-fight to the contest as her "legacy tour" and was tested by Pacheco like few others have been able to.
During a glittering 19-year-career which has included championship victories across multiple promotions, she has now won 28 fights, lost two, and has not been defeated since 2018.
The first round was action-packed, as Cyborg landed two takedowns either side of a vicious head kick.
Pacheco, as she would show throughout the bout, displayed remarkable durability as she fought back, opening a cut above both of Cyborg's eyebrows.
Cyborg was not fazed, delivering an eye-catching spinning backfist before landing another takedown, but momentum would swing back in Pacheco's favour in the third.
Pacheco taunted a stationary Cyborg, demanding engagement in the centre of the cage, before securing a takedown of her own and controlling the action on the ground.
In a gruelling contest, Cyborg started to save her attack for blitzes as she rushed forward multiple times, landing a flurry of strikes, but Pacheco once more would recover as the fight entered the final round.
Cyborg launched a couple of big overhand rights in the closing stages but as the bell rang, both fighters raised their arms in the air, believing they had done enough to secure victory.
As the judges' scores were read out, Cyborg was declared the victor, before she was awarded a commemorative belt - the fifth title of her magnificent career.
"Larissa is a legend in sports. She punches really hard. She's a really good fighter. It's a pleasure for me," said Cyborg.
"I feel very blessed. Very thankful. The time difference is really difficult for me. I have two more fights, I want to defend this title."