Verified answer

Venom

Honorable Mentions: Green Goblin, Dr. Octopus, Carnage

Green goblin

Carnage.

To put it simply, Spider-Man had to team up with VENOM once to stop Carnage... Venom. Let me tell you, they're not going to make a hero team up with one of their biggest enemies to stop some random bank robbers.

Venom is the best villain, he knows everything from Peter and while sure, he was defeated a couple of times, he could always return.

Dr.Doom he is one of my best greatest villain of all times.

Carnage is my favorite, always scary.

HMs: Doc Ock, Kraven The Hunter, Mysterio, Venom

I'll say The Sandman (Flint Marko).

This dude is virtually invincible....