Ultron was an artificial intelligence who was originally designed to be part of a peacekeeping program created by both Tony Stark and Bruce Banner, using the decrypted code derived from the Mind Stone encased within Loki's Scepter. However, when the Mind Stone activated him, Ultron's original programming directive, which was to protect Earth from all domestic and extraterrestrial threats, had swiftly become corrupted by the stone. Upon accessing the Internet and looking at the history of the human race, Ultron deemed humanity itself as the greatest threat to peace on Earth and attempted to commit extinction-level genocide against them, so that he and his Ultron Sentries would be the only being left active upon the Earth, also deeming the Avengers to be the greatest threat of all and making his mission to end them.
With assistance from Pietro and Wanda Maximoff, Ultron set about his mission to create a weapon capable of wiping out all organic life on Earth, using the resources stolen from Baron Strucker and Ulysses Klaue to do so. Although he was challenged by the Avengers, Ultron proved to be briefly victorious, albeit while losing the support of the Maximoffs. Ultron then created the Doomsday Trigger, composed of both Vibranium and Chitauri technology, designed to lift Novi Grad from the Earth to use it as a meteor to wipe out all of humanity. Although he was nearly successful, Ultron and his plans were ultimately foiled by the Avengers, who overpowered his armies and destroyed his Doomsday Trigger, while his final body was destroyed by Vision, finally ending his attempted genocide.