Megatron

Comical, yet ruthless, Megatron is the evil leader of the Decepticon armada with a secretly soft heart. Somewhat of a reflection of his greatest adversary, Optimus Prime, Megatron seeks to control the world at any cost necessary, even allying himself with other baddies, such as Cobra Commander.

History
Megatron hailed from the planet of Cybertron, a distant alien planet where the robotic lifeforms known as Transformers thrived. At some point, his conflict with Optimus Prime found its way to Earth and soon, a three-way conflict involving the Decepticon forces, Autobot forces and G.I. Joe commenced. After a failed duel with Optimus Prime, Megatron was eventually defeated and sent to the dimension in which Magic is Friendship.

Megatron had a mini-version of himself, Mini-Megatron and seemed to, to some extent, worship the almighty god Unicron, the eater of worlds.

At one point, he plotted to, presumably, take over the world with Nightmare Moon.

With the help of Cobra Commander, Megatron stole the Matrix of Leadership and planned to take over the world, however he was defeated by Twilight Sparkle, Rarity and Pinkie Pie firing gun at him.

In 2013, Megatron claimed to have cried when he saw the Coronation of Twilight Sparkle, which he later admitted was his most embarrassing moment.

He presumably had a complicated relationship with Sideways and Starscream.

He really liked Summer and even had a song about it!

Equipment

 * Fusion cannon: Megatron has his own gun known as the Fusion cannon. He toted it while with Nightmare Moon, but hasn't shot it at any ponies.
 * Matrix of Leadership: Megatron once had ownership of the Matrix of Leadership and planned to use it to take over the world, until he was thwarted by twilight Sparkle, Rarity and Pinkie Pie.

Behind the scenes
Megatron is one of the two main characters of The Transformers series. Since The Transformers and My Little Pony are both owned by Hasbro, and since both have comics published by IDW Publishing, crossovers between the series have not been to uncommon. Megatron was sent to a dimension with Lyra Heartstrings, Twilight Sparkle and Moon Dancer during the events of The Transformers vs G.I. Joe, three unicorns when he desired to find Unicron. The multiverse is as cruel as is vast.

Appearances

 * Are You Ready For The Summer?
 * The Transformers vs G.I. Joe
 * "When Worlds Collide"