When Hank Pym first built Ultron, it was with good intentions. However, the robot soon rebelled, hypnotised Pym into believing he had never been made and quickly began upgrading himself (from Ultron-1 all the way through to Ultron-5). When Ultron-5 first headed out in to the world, he was an unnamed character in 1968 in Avengers #54 - and he was under the guise of the Crimson Cowl (who is a character in her own right, having been the name given to Justine Hammer and Dallas Riordan at certain points in Marvel history). The Crimson Cowl actually fought against his "Father" and his fellow Avengers as the Crimson Cowl. It wasn't until he had defeated the superhero team that he unveiled himself to be Ultron.
