I'm sorry but the undertaker??? No way. He has done some basic shit but to say he would've done well in UFC is absurd. Cm punk technically has a "background," too. But anyone with half a brain knows odds are he's going to get his ass beat. Just because taker is a fan, doesn't mean he just be in the ufc and do well.Real Life fighters as in an MMA fighter, boxer, etc.?
Aside from Brock Lesnar and Ken Shamrock(who both competed as MMA fighters already in real life in the UFC), I think Kurt Angle, Rob Van Dam and The Undertaker would have been pretty good fighters in real life. We all should know why Kurt Angle would be a good fighter and both RVD and Taker have martial arts backgrounds(especially RVD).