Underrated Spider-Man villains

Black Cat is one of the under rated though she's a neutral character.

I'd say Scorpion. He was Venom for a time and gave Venom the reputation he still has today. Scorpions and Spiders are related and natural enemies in real life so he could have been Spider-man's best villains. Unfortunately writers made him just some deranged hit man who Spider-Man can take out with ease.