Chameleon (comics)
Created by writer Stan Lee and artist Steve Ditko, the character first appeared in "The Amazing Spider-Man" #1 (March 1963), making him the first member of Spider-Man's rogues' gallery, based on issue publication date, excluding the burglar who murdered Ben Parker (Supercharger was the first Spider-Man supervillain chronologically). He is also well known to be related to Kraven the Hunter. That revealed relationship helped evolve him as a major villain compared to his original depiction of being just a solo villain in the original issue of "The Amazing Spider-Man".
The Amazing Spider-Man
Most of Spider-Man's key villains and supporting characters were introduced during this time. Issue #1 (March 1963) featured the first appearances of J. Jonah Jameson and his astronaut son John Jameson, and the supervillain the Chameleon. It included the hero's first encounter with the superhero team the Fantastic Four. Issue #2 (May 1963) featured the first appearance of the Vulture and the Tinkerer as well as the beginning of Parker's freelance photography career at the newspaper "The Daily Bugle".