One cannot do without them: whenever one of them apparently died, other persons assumed the mantle in his stead.

(In chronological order)

(1) The Vulture
http://www.supermegamonkey.net/chronocomic/entries/amazing_spiderman_2.shtml

(2) Doctor Octopus
http://www.supermegamonkey.net/chronocomic/entries/amazing_spiderman_3.shtml

(3) The Lizard
http://www.supermegamonkey.net/chronocomic/entries/amazing_spiderman_6.shtml

(4) Mysterio
http://www.supermegamonkey.net/chronocomic/entries/amazing_spiderman_13.shtml

(5) The Goblin and his legacy
http://www.supermegamonkey.net/chronocomic/entries/amazing_spiderman_14.shtml

(6) The Hunter and his family (the Kravinoffs)
http://www.supermegamonkey.net/chronocomic/entries/amazing_spiderman_15.shtml