I would have thought he was the most badass for what he went through in the original games but I just started playing the latest one... Wow! Yeah, Doomguy is going to be the most badass ultimate survivor.
Now the quality
of that survival would be questionable at best. Sure the demon hoards have been crushed and driven from the earth realm but I don't see Doomguy planting crops or repairing machinery anytime soon.
So if the question/definition of survival here is existing
then Doomguy has my vote. Otherwise, I dunno... Wolverine or Deadpool?