Megatron

In Iacon, D-16 is a miner without a transformation cog and Orion Pax's best friend. The two break rules together, get punished and follow Alpha Trion's message to the surface. There they learn that Sentinel Prime, the leader D-16 looked up to, murdered the Primes and stripped the miners of their cogs. With the Primes' cogs, both of them can now transform.

The truth changes D-16. He beats Starscream in a challenge and takes over the High Guard, Iacon's rebels. In prison, he learns Sentinel stole the cog of his hero, Megatronus Prime, and is branded with that face. Growing more violent, he argues with Orion over whether to kill Sentinel and, in the struggle, accidentally shoots his friend. He kills Sentinel, takes Megatronus's cog and renames himself Megatron. Defeated by Optimus and driven out of Iacon, he turns the High Guard into the Decepticons, with Megatronus's face as their emblem.

In the Michael Bay saga, Megatron finds the AllSpark on Earth but ends up frozen in Arctic ice. In 1897, explorer Archibald Witwicky stumbles on him and accidentally activates his navigation system, which imprints the route to the cube on the explorer's glasses. Sector 7 takes the body, keeps it frozen and studies its technology for decades.

In the present day, Frenzy frees him at the Hoover Dam. Megatron chases the AllSpark to Mission City, where he takes on Optimus. Sam Witwicky rams the cube into his chest, and Megatron dies along with the AllSpark.

Two years later, the Constructicons use an AllSpark shard to revive Megatron on the ocean floor. He goes back to serving his old master, the Fallen, and hunts Sam, who carries the map to a new Energon source in his head. In a fight with Optimus, Megatron kills him. In Egypt he kills Sam, whom the Primes bring back. Wounded by Optimus, he flees with Starscream.

In Dark of the Moon, a still-wounded Megatron strikes a deal with Sentinel Prime, who uses the Pillars to bring in hidden Decepticons and invade Chicago. During the battle, wanting command back, he takes down his ally and offers Optimus a truce. Optimus refuses, tears Megatron's head off and executes Sentinel.

Five years later, the company KSI uses Megatron's remains to build robot soldiers. The prototype Galvatron breaks free of human control: he's Megatron reborn. He escapes Hong Kong vowing to return. Frank Welker, the 1984 cartoon's Megatron, voices the new body.

In The Last Knight, back to the name Megatron and still voiced by Welker, he allies with the sorceress Quintessa. The Decepticons steal Merlin's staff, and Sir Edmund Burton dies at Stonehenge trying to stop him. In the final battle on Cybertron, Optimus defeats Megatron.

In the 1984 show, Megatron turns into a pistol and leads the Decepticons who wake up on Earth after 4 million years. He's a dictator willing to drain Earth's energy the way he drained Cybertron's, with Starscream forever scheming to take his place.

In 2005, Megatron attacks Autobot City and duels Optimus Prime, leaving both mortally wounded. Starscream dumps his dying leader into space. There, Unicron, a planet-sized robot that devours worlds, offers him a new body in exchange for destroying the Matrix of Leadership. Megatron agrees and becomes Galvatron, voiced by Leonard Nimoy. He returns to Cybertron, kills Starscream during the traitor's coronation, retakes command, kills Ultra Magnus and seizes the Matrix. In the end, Unicron swallows Galvatron and the Matrix.

In Transformers: Prime, Megatron returns from three years of exile with Dark Energon, which can turn dead Transformers into Terrorcons. When Unicron wakes in Earth's core, he teams up with the Autobots to stop it, then manipulates an amnesiac Optimus. Later he tries to use the Omega Lock to turn Earth into a mechanical planet. In the final battle he shoots Bumblebee, who comes back and kills him with the Star Saber.

In Predacons Rising, Unicron reanimates Megatron's body to destroy Cybertron. Once Unicron is sealed away for good, Megatron regains control of himself, disbands the Decepticons and goes into exile, far from Cybertron.

The toy came from Japan's Microchange line, where he was a hero. In the U.S. he turned into a Walther P38 pistol, and later toy laws forced other alt modes. Bob Budiansky came up with the name. In Marvel's comics he's a former gladiator who started Cybertron's civil war. The Beast Wars Megatron is a different robot who took the name in tribute to the original.