Mike Tyson's character from Ip Man 3 defies the "most complete fighter in the world". Boyka gets his knee healed before the fights
1: Sanda Rules, because let's be honest, UFC rules would favor Boyka too much. For those who don't know, Sanda allows punches, kicks and throwing techniques, with boxing gloves. Example here.
2: Boxing rules.
3: Khazan arena rules.
Bonus: Any match that Frank loses, he gets a rematch with the injured Boyka from Undisputed 3.
Bonus 2: Thoughts about Frank facing other fighters from the Undisputed-verse, especially Chambers and Turbo?