It's pretty clearly Ubereem during and before the Brock fight. At his best, he would beat any fighter -- any man in history -- on any night.
It would be absolutely fucking awesome if someone as talented as Fedor or DC or Jones hopped onto the same horse meat diet that Overeem was on. Especially Jones because he really has the frame size to benefit from it and he was only like 25 years old at his best. A 5'9" guy can only get so big, even on horse meat and 40 is still 40. 6'5" 84" reach frame on Ubereem level horse meat with the most talent in history and a 25 year old body with a high fast twitch muscle fiber ratio... haha. The level of such a fighter would be mind blowing.
Imagine if there was no weight limit and Jones came in like a prime 350 lb shredded Bob Sapp. He has the same frame, he could do it.