There is a running trend concerning Ultron that the child always ends up betraying its creator. When Hank Pym created Ultron, his creation turned on him. When Ultron created The Vision, his creation also turned on him. Another creation of Ultron that betrayed her master was Jocasta.
Jocasta's first appearance came in The Avengers vol.1 #162 by Jim Shooter, George Perez, Pablo Marcos, Denise Wohl, and Don Warfield, in which Ultron wiped Ant-Man's memory and sent him to attack the Avengers. After that battle, Ultron appeared to kill Captain America, Scarlet Witch, and Beast and kidnapped Wasp.
Ultron had one simple plan to transfer Janet Van Dyne's life-force into the metalloid body of a robot. Ultron explained to Pym they needed to save Wasp's life by fixing her body while her life-force was safe in the other body. His real motive was to use Jan's mind to create his own mate in Jocasta, a move that Pym could never reverse if completed. It was the Oedipus story all over again. The son murdered his father and married his mother, with Ultron turning Jocasta into his version of Jan. However, a swarm of ants altered the Avengers to the experiment's location. Black Panther believed it was Jocasta, with Jan's mind partially in her, that called out for help, betraying her creator.
In Avengers #170 by Jim Shooter, George Perez, Pablo Marcos, and Denise Wohl, Hank had been studying Jocasta when she suddenly roared to life. Ultron remotely activated her, and her programming was set to return to him. There was still a sliver of Jan's essence in her, though, and it was enough to give her a personality and emotions. She wanted to leave, and the Avengers attacked her. However, Iron Man and Captain America stopped them so Jocasta could lead them to Ultron. It was at this point that she betrayed Ultron and helped the Avengers stop him. After she helped the team survive the "Korvac Saga," Jocasta joined The Avengers for a short time. She ended up leaving before they could make her an official member and wandered the country.
Jocasta faced a major change years later when she began to seek an ethical protocol for all robotic lifeforms. She took this journey with her new boyfriend, Machine Man. However, the two of them had differing opinions when she supported Tony Stark's idea of creating Project eScape. Robots could live in a virtual world and have a life like any human in that society. Machine Man was all about militant mecha-activism, and Jocasta wanted to experience life as a human being. This all led to the events of Iron Man 2020 and the Robot Revolution.
Arno Stark, Tony's brother, took control of Stark International and helped rebuild Jocasta in a less humanoid body. He then equipped her operative system with code forcing her to become more compliant with human orders, known as a submission code. When word got out that Arno planned to do this to all robots, the A.I. Army attacked, and Machine Man ending up facing off with Jocasta.
He saved Jocasta, and once again, she took on the role of a hero and helped stop Arno's plan by freeing Tony Stark and placing the submission code in Sunset Vain -- who turned out to be a robot herself. This made Sunset take all the blame for the actions of the A.I. Army and Arno Stark and ended the war once and for all.