An evil, sentient robot created by Dr. Henry Pym. Somewhere along the way, the robot became evil, and is a recurring bad guy intent on destroying Dr. Pym and the Avengers.
He has been defeated a number of times, only to keep reappearing. One of the more recent forms he has adopted is a robotic body made out of the indestructable metal Adamantium, so he's now really hard to stop.
He made the being now known as the Vision, who ended up being a superhero.
He lives in the Marvel Comics universe.