Mac Gargan.

A.k.a The Scorpion. Paid to go through an experimental animal mutation therapy by J. Jonah Jameson, Mac went insane. But, he also got super powers. Not a bad pay off. His costume has changed over the years, making it more Scorpion like. I stuck with the original. Recently he's been delegated to a sort of second tier Spidey bad guy. Actually, he's the new Venom... Not for me. For my money, he's still the same wall smashing lunatic that I loved as a kid. I'll get you Spider-man!

Sergei Kravinoff.

Kraven the hunter. The final member of the Sinister Six. This famous big game hunter has given Spider-man a pile of trouble over the years. I still remember the shock of reading " Kraven's Last Hunt ". Besides Mike Zeck's beautiful art, I was blown away ( I know, bad pun..) with Kraven taking his own life. If you haven't read that series, I highly recommend it. I almost wish he was still around.