Carnage is the deadly!!! But compared to Venom's enimity with Spidey... it is nothing. Carnage loves killing, every kill is sweet for him. Venom loves killing too, but the death of Spiderman and Carnage ranks way above his other kills. His intimate enimity makes him the deadlist of Peter parker's foes and my favourite of course.
If we're talking about best Spider-Man villan I would have to say Venom. Brock not only hates Parker, but so does the symbiote. Venom also spends time hanging around Parker's family and house just to mess with his mind. Also, he doesn't show up on Spider-Man's spider sense and that just makes him so much harder to fight.
If we are talking best bad guy period, Joker, no doubt about it. Dark, twisted, demented as hell, and extremely funny at times. The only man that Batman truly fears (and that's saying quite a bit).
Yes, The Joker is the only villain that beats Ock.
He's like the scariest (and funniest) villain in the known comic universe, and he doesn't even have superpowers. That's how good The Joker is.
It also helps if your character is voiced by Mark Hamill in the cartoon and played by Jack Nicholson in the movie. Best villain, ever.