I have three.
From the 90's it was The Phenom. He was the first BJJ blackbelt who liked to bang and knock people out cold. BJ, Nick, and Nate have followed suit. Definitely the Mike Tyson of MMA.
Early to late 2000s it was Crocop. After watching Tito, Coleman, Hughes, Randy, and basically all the wrestling based fighters take over it was refreshing to see a one dimensional striker kick peoples' heads off...literally.
Presently the MW Kingpin. He is truly one of the few if not the only fighter that I've witnessed able to put EVERYTHING together in a very calculating way. He does not fight just to win. He fights to end you decisively...when he wants to.
Marcus Aurelius: Tell me again, Maximus, why are we here?
Maximus: For the glory of the Empire, sire.
Baked, not fried... the healthy choice.