Does the question refer to who has the biggest penis or who is the biggest a**hole?
If it's in reference to the size of one's Johnson, I can only speculate, and I really don't want to.
If it's the latter, I'd go with Tito Ortiz. But, he tries to be that way just to hype fights. I think he'd be pretty cool to hang out with.
Nick Diaz looks like he'd be real nasty if he didn't like you. On the other hand, I think he'd treat you like gold if he liked you. He seems very passionate about what he likes and believes in.
Probably Dana White. A lot of people have a problem with him. Tito did. Frank Shamrock has been abolished from the UFC website, erased from their history even though he was an undefeated middleweight champion.
That's a d***.