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".
Alpha Centurion
During the "Zero Hour" storyline, Superman was transported to an alternate timeline where he stumbled upon a Metropolis whose hero was the Alpha Centurion, a man named Marcus Aelius from Ancient Rome who had been trained by an alien race called the Virimiru only to return centuries later. Initially joining the gathered heroes, the Alpha Centurion went on to join Extant and Parallax in fighting against the heroes of the DC Universe, siding with Parallax as he promised to restore Alpha Centurion's apparently lost timeline. After the heroes had to restart existence with a new Big Bang, all alternate realities ceased to exist and this Alpha Centurion was no more.