Galvatron

Galvatron is the alternate, more powerful form of Megatron. He's the secondary antagonist in Transformers: The Movie, and the main antagonist in the other Transformers series.

Transformers: the Movie
After Megatron was badly injured by Optimus Prime and betrayed by Starscream, he comes across Unicron. Unicron asked him to destroy the Autobot Matrix of Leadership, but Megatron refused. Unicron offered him a new body and new troops to command. At first he refused, but when Unicron attempted to kill Megatron, he accepted his terms. Megatron was repaired, modified and was renamed Galvatron. After Galvatron acquired his new henchmen, Scourge, and Cyclonus, and acquired a new ship, he went to Cybertron to reclaim the throne, and kill Starscream. After he killed Starscream, all the Decepticons declared him as their new leader.

Galvatron, along with a few other Decepticons went to Earth and attacked the Autobots. Galvatron chased the Autobots into space and attempted to destory their ships. he managed to destroy the shipwith Hot Rod, Kup, and the Dino-bots. To prevent the other Autobot from being destroyed by Galvatron, Ultra Magnus used the Emergency Seperation. This cause 1/4th of the ship to seperate from the ship. Not supecting a thing, Galvatron destroyed the lower portion of the Ship. but Unicron knew that the Autobot were still alive, he decided to torture Galvatron for failing.

When Galvatron went to Unicron, he asked why did he tortured him. Unicron told him that the Autobots were hiding on the Planet of Junk. So Galvatron decided to send a small army of Decepticons to attack the Autobots. Ultra Magnus attempted to open the Matrix, but it wouldn't open. After being denied the Matrix, Galvatron sent the sweeps to exterminate him. After Magnus died, Galvatron decided to use the Matrix against Unicron and make him his slave.

Know Galvatron betrayed him Unicron transformed into his robot mode and decided to destroy Cybertron slowly. Knowing that Cybertron was about to be perished, Galvatron decied to join the fight and fight Unicron, but Unicron grabbed Galvatron and ate him. When the Autobots managed to get inside Unicron, Hot Rod got seperated from the others and encountered Galvatron. At first Galvatron wanted to help the Autobots destroy Unicron, but Unicron tortured Galvatron's mind and told him to destroy Hot Rod and then the Matrix. It seemed that Galvatron was about to kill Hot Rod, but when Hot Rod grabbed the Matrix, he transformed into Rodimus Prime and threw Glavatron out of Unicron.

Trivia

 * Galvatron is voiced by Lenard Nimoy in the Transformers: The Movie.