the x-men, friends of humanity comes to mind.
but on this list, probably batman because his opponents are all certifiable.
a archetypal spider-man villain is a guy doused with chemicals/rays then given an animal suit. batman on the other hand fights guy that usually fit a certain type of psychosis or other numerous mental problems and gets their kicks by preying on the public.
punisher fights mercs and crime lords, money is their usual modus operandi.
so yeah, bats imo has the worst opponents, gotham is such a filthy crime ridden city that if and when batman is not there, crime levels go through the roof.
Batman by far. I think most people would get depressed and quit the buisness if they had to see the kind of stuff he has. Child killers and such. DD and Punisher more or less fight the same type of criminals, generally organized crime or people with a actual goal in mind.
Maybe a better match up for worst scum villains would be Spawn, who has had to deal with folks just as f'ed up as Batman.
besides killing all the jews hitler wasn't that much worse than any other dictator. And he at least had some reason to kill the jews. they were messed up reasons but its something. Joker kills ppl just for fun. If he was running a country he'd kill everyone who wore orange on tuesdays just because he could.
Most of the other criminals commit crimes for greed usually which is pretty basic evilness.