The 1986 film transforms Megatron into Galvatron, giving him a new body and a new master. Image source: The Optimus Prime Experiment.
Revenge of the Fallen returns Megatron to life while placing him beneath another ruler. Image source: The Optimus Prime Experiment.
Optimus Prime and Megatron in illustrated combat. Artwork from the site’s Transformers hub. Image source: The Optimus Prime Experiment.