Unicron

Unicron was a planet-sized Transformer who devoured worlds and played the primary antagonist in Transformers: The Movie. He was voiced by Orson Welles - this was actually his final film role before his death in 1985.

According to the original animated series episode "Call of the Primitives," Unicron was created by a being called Primacron to destroy the Universe for him to remake in his own image. Unicron was supposed to do this alongside a counterpart, Tornatron, which consumed stars.

The Transformers comic book identified Unicron as a deity-like being that opposed Primus, the forefather of the proto-Autobots and Decepticons. The two fought until Primus dove into an asteroid, tricking Unicron into doing the same, and both combatants became trapped. As Primus fashioned his asteroid into a planet supporting mechanical life, Unicron fashioned his into a replica of his original form, which had the additional ability to transform into a planet-like form. In this form he is able to consume entire planets (sometimes refered to as Planet Killers)

Unicron made his first appearance in Transformers: The Movie, dramatically consuming a planet supporting mechanical life (similar to Cybertron), of which only a single inhabitant survives. Unicron later appears before the battered Megatron, demanding that he destroy the Autobot Matrix of Leadership, "...the one thing, the only thing, that can stand in my way." To allow him to perform the task, Unicron "reformatted" him and a half-dozen other severely damaged Decepticons and provided them with a starship. When Galvatron returned with the Matrix, he tried to open it and use it against his master; but he had underestimated Unicron, who dramatically transformed from a planet-consuming machine-planet into a planet-destroying humanoid, and proceeded to lay waste to a swath of Cybertron.

The Autobot Hot Rod claimed the Matrix from Galvatron and managed to open it within Unicron, and the waves of energy systematically destroyed him. Uttering one last line: "Destiny... you cannot... destroy my... destiny..." Unicron exploded, and his disembodied head was trapped in orbit around Cyberton, a grisly monument to the moons that he had consumed.

Unicron is feared by most of Cybertron, even into the distant future, so much so that the Vok's (AKA "The Others") use of his visage during the Beast Wars was enough to instill cold terror into Optimus Primal.

For many years the toyline had no Unicron toy, despite a number of prototypes. This changed in 2003 when one was released.