Both are known to take on other forms to alter their powers (Frieza has numerous transformations which increase his power while Megatron can transform into a gun, tank, jet, or stealth bomber).
Both are associated with the color purple, with it being a part of their designs and energy attacks. Both are also constantly fighting a race of alien heroes (Saiyans and Autobots respectively) to determine the fate of the Earth, although they both have a history of temporarily teaming up with the protagonists to take on a common foe. They are enemies of their series' main protagonist whom are considered their equals in combat (Goku and Optimus Prime, respectively), and are responsible for the destruction of their home planet (Vegeta and Cybertron, respectively), which ended up indirectly creating their foe in the process. Two selfish, arrogant, ruthless, powerful alien warlords who lead armies to conquer planets and accomplish their goals through either deception or brute force.
