The character is the big bad in the upcoming second Avengers film.
Though we're introduced to Ultron in the "Masters of Evil" arc, we don't find out his origin until four issues later in Avengers no. 58. Hank Pym, a.k.a. Ant-Man, is Ultron's creator — and he didn't even know it.
Pym was one of Marvel's most troubled superheroes. His powers — changing his size — weren't as flashy as Thor's or Iron Man's. And his intelligence wasn't as revered as Reed Richards's. He was the Ringo of the Avengers.
"His history was largely a litany of failure, always changing guises and switching back and forth from research to hero-ing because he wasn't succeeding at either," Jim Shooter, a former editor-in-chief at Marvel wrote on his site, explaining Pym's shortcomings. "He was never the Avenger who saved the day at the end and usually the first knocked out or captured."
Ultron's origin was another indication that Marvel was changing the way it thought of bad guys and the importance of where evil comes from. Marvel wanted to make it clear that villains' beginnings mattered and that it benefits storytelling and superheroes when a story's antagonist has nuance and depth.