Megatron

Megatron was a Cybertronian warlord and the original leader of the Decepticons. He owned a fusion cannon and could transform into a gun.

He fought Zev Raregroove, Malygos and Iron Man, and was subsequently destroyed.

Virtual Megatron
Another version of Megatron appeared as a character in Transformers: Revenge of the Fallen: The Game, which was one of the many scenarios that were programmed into Darkmount's Virtual Reality. This Megatron was fighting Bumblebee in a level called Desert Massacre, when Muta, who at the time was being beaten up by the contents of Blackout's computer, appeared. Bumblebee then paralyzed Muta, allowing Megatron to KO him and blast Muta into the Autobots' war room.

He ceased to exist when the VR was deactivated and Darkmount was destroyed.