The Sinister Six
"After Suffering three defeats at the hands of Spider-Man, Doctor Octopus realized that he needed help against the web-slinger. Her got in touch with every superpowered villain who had battled the wall-crawler. In the end, five other criminals heeded Ock's call - the Vulture, Electro, Kraven the Hunter, Mysterio, and the Sandman." -Spider-Man: The Ultimate Guide
In the place of Kraven, when the super-villian team has been reformed, both Hobgoblin and Venom have filled in.
Due to the team's inability to function as a well-oiled unit, Doc Ock's plan of leadership involved using each member's reckless ambition to destroy the wall-crawler. They faced Spidey in specifically chosen locations with the plan that one would eventually destroy him.
During one of their most famous unions, the Six comandeered a satellite controlled center belonging to HYDRA. Octavius's plan was to use the satellites to bombard the Earth with deadly radiation.
Spider-Man formed a union with Nova, Hulk, Deathlok, Ghost Rider, the Fantastic Four, and Solo and managed to subvert the Sinister Six's plan. When things seemed lost, Doctor Octopus released an other-demensional monster called Gog to defend them. But he was defeated as well.