Computron is a villain from Ben 10: Ultimate Alien, He is a robot that was imprisoned in Dimension 12 and he's an enemy of Captain Nemesis.
His first appearance was in Hero Time.
In Hero Time, Captain Nemesis released Computron along with some of his Computron's minions from Dimension 12 to try to prove himself to a better hero than Ben Tennyson. When Computron and his minions were released from Dimension 12, Computron and his minions start attacking the some workmen in sight, but Captain Nemesis came to stop Computron and his minions. When Captain Nemesis was busy fighting Computron, Ben as Armodrillo destroy Computron's minions causing him to get the most credit while Captain Nemesis only defeated Computron by punching his head off.
In Girl Trouble, Computron minions attempt to avenge Computron's destruction by set up a bomb that will destroy the Earth, but their plan failed when Kevin Levin disarm the bomb.