Tyson Fury says the boxing world should "laugh" at him if he is beaten by Francis Ngannou in their fight in Saudi Arabia on 28 October.
Heavyweight world champion Fury, 35, will face former UFC heavyweight champion Ngannou, who has no professional record in boxing.
Briton Fury's WBC title will not be on the line against against Ngannou.
"I need to be on my A-game," Fury said. "There's more on the line now than in a boxing fight."
Fury and 37-year-old Ngannou came face-to-face at a news conference on Thursday in London, which was heavily saturated by references and compliments to Saudi Arabia.
The country has been criticised for using sport to sportwash their image and have reportedly paid millions to bring Fury's bout with Ngannou to the region.
Their contest will take place under the official rules of professional boxing, with three judges ringside adopting the 10-point must system.
Fury is a two-time world champion and defeated Derek Chisora at the Tottenham Hotspur Stadium in December to extend his unbeaten record to 33 wins and one draw.
"If I lose to an MMA guy I'll never be able to show my face in public again," he added. "It's going to ridicule me - people will chuck it at me forever.
The Morecambe fighter's decision to fight boxing novice Ngannou rather than a credible opponent has been lambasted by purists, particularly after super fights against Anthony Joshua and unified champion Oleksandr Usyk could not be agreed.
"There's more riding on this than ever before," Fury said.
"Whether the media want to take it as a joke, make no mistake Tyson Fury will leave zero stones unturned and I will come in as my fittest and strongest I've ever been to defeat this man.
"If I'm not and I get knocked out, then I want you all to laugh at me. That's what I want, because I deserve it."
'I'll be hunting for this guy's head'
French-Cameroonian Ngannou held ambitions to be a boxer before venturing into MMA. He is known for his punching power and knockout ability and will be trained by boxing Hall-of-Fame star Mike Tyson, a man Fury was named after.
"Too bad for him, Mike Tyson loves me more than him," joked Ngannou.
He became UFC heavyweight champion in 2021 and defended once before his relationship with the MMA promotion and its president Dana White broke down.
"I have had these dreams since I was a kid to become a boxer today," he added. "It's not just that I'm going to box, but I am going to box the guy on the mountain."
Earlier this year Ngannou joined MMA promotional outfit PFL who, unlike the UFC, do not contractually prevent fighters from freely competing in other combat sports.
He added: "Nobody knows exactly what's going to happen. But what I do know for sure is I am going to be out there hunting for this guy's head, to take it off."
Ngannou's MMA record has see him enjoy 17 wins in 20 fights, with 12 knockouts.
He said: "What will happen at the moment that guy hits the floor and doesn't stand up?
"Will I be the best boxer in the world? If you take out the number one, you are the number one? I think so."
Having exchanged several compliments, the news conference became slightly more intense when Fury said he would welcome an MMA fight with Ngannou in the future.
"Firstly I will beat you in a boxing ring and then I'll kick your ass in a stage," he said - a comment which appeared to rile Ngannou.
The light-hearted nature of the conference then returned at the obligatory face-to-face meeting. Fury took off his top and encouraged his rival to do the same. A bemused Ngannou refused.
Analysis - winning hardcore fans over will be tall order
Billed as the 'battle of the baddest', Fury-Ngannou is a contest between two elite combat sport athletes. But many feel the main bout - and the event as a whole - falls into a similar bracket as YouTuber or entertainment boxing.
There was a brawl involving British heavyweight rivals Fabio Wardley and David Adeleye - who will fight on the undercard - at the red carpet event, with Wardley left bleeding after a cut to his face.
Inside the venue, stars from British reality TV shows Love Island and The Only Way is Essex mingled with former footballer Rio Ferdinand.
After the conference began an hour after the scheduled start, Fury said: "I don't know what to say."
He then stood up, walking up and down the stage while delivering a long monologue.
He called Ngannou a dosser, made X-rated references and repeatedly paid respect to the Saudi government.
Team Fury insist this is a serious fight and the champion will undergo a 12-week training camp in preparation.
But many traditionalists feel he is partly to blame for fights with Usyk and Joshua not materialising and wanted to see him against a live contender, not Ngannou.
Fury will always entertain and this fight will appeal to a wider audience, but winning over those hardcore boxing fans will be a tall order.