Ultron was a genocidal machine, but Marvel reveals Iron Man could have turn it into a hero if he put MORE of himself into the creation, not less.
Marvel's Iron Man is an egotistical braggart, but his ego was just the thing that could've made Ultron into a hero. The villainous machine is one of the Avengers' most frequent foes, fighting to conquer the planet, destroy it outright, or enslave organic beings while he creates a new world made of machines (or any combination of the three). But in Extraordinary X-Men #9, Marvel all bit admits that Stark could have turned Ultron into an Avenger itself - if he just put more of his own mind into the mechanical monstrosity.
The origin of Ultron in the comics is quite different from the origin in the Marvel Cinematic Universe, specifically 2015's Avengers: Age of Ultron. In the comics, Ultron is primarily a creation of Hank Pym aka the first canonical Ant-Man. Upon activation, Ultron developed a pure, irrational hatred of humanity - especially for his creator and "father" Pym. Perhaps because of this, he also developed an interest in the Wasp, while simultaneously creating the Vision to fight the Avengers. Vision eventually became part of the Avengers and a force for good, but Ultron did not.
In Extraordinary X-Men #9, new mutants are more valuable than ever since the Terrigen Mists - the gaseous substance that grants the Inhumans their powers - were found to be poisonous to mutants. A group of mutants carrying embryos are beset with foes all around them - until they find a colony of artificial intelligences led by the Stark-Self, a highly-advanced AI housed in a body who's faceplate looks suspiciously like Iron Man's. Though helping the mutants is against the law in this new dystopia reality, the Stark-Self eventually agrees to aid them, because "...The Stark-Father was an ally to the X-Men and we have calculated that he would also wish to be an ally to you were he still flesh...no matter the cost."
The Stark-Self is an indication of Ultron's final fate...were he created by Tony Stark and not Ant-Man. If the adage is true that every creator infuses their creations with a sliver of their own selves, then the problem behind Ultron's creation becomes readily apparent. Iron Man's creations worship him (as he does himself), but Hank Pym's creations are the personification of his worst attributes.
Tony Stark's desire to create new and better AIs to help humanity coalesce into the Stark Self, and this ultimately aids mutant-kind as well. The fact that the Stark Self acted not for the purpose of its own self-preservation but for the sake of those in need means Tony could have programmed Ultron to act in the same manner. Alas, Ant-Man's own failings meant that an Iron Man-created Ultron simply wasn't meant to be.
