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.
__________________ "Happiness is a lie. Life is horror. The light is always dying all across the universe. The last star will flicker out someday, when it does, all that remains is shadow. And I will be its king!"'-Amahl Farouk
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.