Not stamina, healing factor or pain tolerance, just hard durability.
You mean simply how tough their outer shell is essentially?
Hmmm my best guess.....
Hulk(classic) I prefer this version over the healing factor
I know Luke Cage is suppose to have nigh impenetrable skin, but I'm still not sure where he'd rank on this list?
I don't think that Ironman, Thing, Cage, Wonder Man or Collossus would survive even one punch from Mangog. Thor took 30 or 40 and kept coming back.