By what metric? Actual number of kills? Total power? Against Spidey specifically or in general? There's also the question of where we draw the line of who's in his rogues gallery. He's fought most of the Marvel universe by this point.
Idol mentioned some with the most potential. But Carnage has racked up more kills than all of those combined. And someone like Morlun probably has the most raw power.
By times one villain went off the charts and became an event villain: Carnage.
By bodycount: Carnage or Morlun.
By history, status and personal stuff it would be either: Green Goblin or Doc Ock.
By simple power level:
Carnage (Carnage U.S.A.)
Judas Traveller (Pre-Retcon)
Spider Queen
Morlun
Solus
Norman Osborn (Super Adaptoid)
Kuhul Ajaw
Regent (full hero tubes)
Originally posted by cdtm
Doctor Octopus. Spider agility/strength is virtually useless against those arms.
Well he has beaten ock physically many times. I went back in the old issues and remembered how physically dominant the lizard was. Spidey would hurt his fists punching Connors and he no sold the shit out of him.