Megatron (Generation One)

"Ah. I would have waited an eternity for this. It's over, Prime."

- Megatron after mortally wounding Optimus Prime.

Megatron, later known as Galvatron, is the main antagonist of the Transformers franchise, serving as the main antagonist of the original 1984 cartoon, The Transformers. He is the founder and leader of the Decepticons, and the arch-enemy of his twin brother Optimus Prime and all of the Autobots.

Marvel Comics
Megatron was a gladiator from Tarn, who sought to turn Cybertron into a cosmic dreadnaught. To win his war for conquest, Megatron's Decepticons developed the art of transformation. Reawakening on Earth in 1984, Megatron was ousted from command by Shockwave, and their power struggle continued for sometime until Optimus Prime killed himself in a video game duel.

Refusing to believe his nemesis was dead, Megatron committed suicide by blowing himself up on a space bridge. However, the explosion had merely deposited him in the Dead End region of Cybertron, where he wandered as an empty, with no recollection of who he was.

After regaining his memories, Megatron forced Ratchet to turn Starscream into a Pretender, but the ploy failed and the two were grotesquely fused in a trans-time dimensional portal explosion. Fixit separated their bodies but the two remained in stasis aboard the Ark. They reawoke when Galvatron, a future version of Megatron, attacked, and Ratchet crash landed the ship.

In one universe, Cobra rebuilt Megatron into a tank, and he allied with Optimus against Jhiaxus, his Cybertronians, and the Swarm. In another, fifteen years of peace passed before Megatron rose again. In a third, he woke up in 1994, and proceeded to lay waste to the Earth, awaiting the day Optimus Prime would return.

1984 Cartoon
Megatron was responsible for bringing Cybertron out of its Golden Age when he restarted the Autobot/Decepticon civil war nine million years ago. Among his first actions was the fatal wounding of a young dock worker named Orion Pax, who was rebuilt to become Megatron's mortal enemy, Optimus Prime.

Megatron's forces boarded the Autobots' spacecraft when it was on a mission to search for new sources of energy on other planets, and was knocked offline like all the other Transformers when the craft crashed on prehistoric Earth. When both factions reawakened in 1984, Megatron made it his mission to pillage all of Earth's natural resources and enslave its populace, with the goal of revitalizing Cybertron and dominating the entire universe.

His plans were by turns cunning, wicked, outrageous, and often, utterly, utterly ludicrous. In 2005, Megatron faced off with Optimus Prime in a battle at Autobot City, during which he fatally wounded the Autobot leader, but not without taking severe damage himself. Cast adrift into space, Megatron was found by the planet-eater, Unicron, and recreated as Galvatron. In other timelines which branch out of this one, Megatron became a Transmetal, ordered the murder of a puppy, and years after his transformation into Galvatron, became Megatron once again, in various powered-up forms.

The Transformers: The Movie
Megatron is the secondary antagonist of the film. Taking several years after the cartoon, Megatron wages a full-scale, geniusly orchestrated assault on Autobot City, crippling the Autobot's ranks and killing several high ranking warriors. When Optimus Prime arrived to the battle, he gunned down almost every Decepticon singlehandedly before taking on Megatron himself. Though Optimus got the upper-hand and was readying to execute his nemesis, the Autobot Hot Shot jumped in the way when he noticed Megatron was reaching for a firearm. Megatron managed to incapacitate Hot Shot and mortally wound Optimus before the latter punched the Decepticon commander off the peak of Autobot City. Prime later died from his wounds. Soundwave recovered his fallen leader when the Decepticons began to retreat, but Starscream eventually threw Megatron's wounded body into space to rust before taking the place as the Decepticon leader. Floating in the voids of space, Megatron was summoned by the omnicidal chaos god Unicron where the former was forced to become the latter's apprentice and enforcer. In return, Unicron gave Megatron a new body and titled him as Galvatron.

Beast Wars
The original Megatron appears in Season 2 of Beast Wars, where it is revealed that the current Megatron was acting on his predecessor's orders.

Later on, the original Megatron makes a physical appearance in Season 3, where the Predacon Megatron takes the original Megatron's spark, making the newer Megatron obtain his dragon form. However, in a deleted scene, in the series finale, the original Megatron's spark is placed back into his body.

Megatron also has another form in the G1 series named Galvatron, a new body given to him by Unicron.

All Hail Megatron
See article: Megatron (All Hail Megatron)

All Hail Megatron is an alternate-reality that was modeled after Generation One, published as a series of comic books. In this reality, Megatron and the Decepticons won quickly after defeating the Autobots back on Cybertron. The U.S. Military is unable to handle the situation with the Decepticons. All Autobot attempts to resist Megatron failed, leading to evil winning over justice.

Personality
Megatron is the commander of the Decepticons, traditional enemies of the heroic Autobots. In almost all variations of the cartoon, comic books and movies, Megatron is depicted as one of the Autobot's most powerful and relentless opponents. In many ways Megatron could be considered an evil counterpart of Optimus Prime. Whereas Optimus has compassion for humanity, Megatron sees them as pawns and slaves. Megatron can be seen as a ruthless military leader and unlike many villains he was not originally depicted as insane or anarchic in nature - simply being overly aggressive and power-hungry but always having a reason behind his actions (even if others often couldn't understand them).

Like many archenemies Megatron and Optimus Prime have an odd sense of respect for one another despite fighting each other to the death. There have been times where the two leaders have acknowledged (at least to themselves) that if it wasn't for their differences in ideology they could of been friends - a fact that saddens Optimus Prime but is actually seen to be rather amusing to Megatron. (This is in fact very similar to the relationship between Magneto and Professor Xavier.)

Trivia

 * In every Transformers variations, he is the Decepticon leader. However, in the live-action films, The Fallen is the true ruler as The Fallen is founder of Decepticons. But Megatron still has control over the Decepticons.
 * He is the most powerful Transformer and considered the most challenging Decepticon, except in the first Transformers series and the Unicron trilogy of Energon, Armada, and Cybertron, where Unicron is considered the most powerful Transformer.
 * He is the arch-enemy of every Autobot, especially Optimus Prime.
 * His leadership of the Decepticons is often challenged in the Generation One series and the show Transformers: Animated by the traitor Starscream. In the G1 series' first TV show, Megatron trusted Starscream for the first two seasons, but in the G1 movie, he was transformed into Galvatron and destroys Starscream, but he returns as a ghost and torments Galvatron.
 * Megatron will search for a prized possession if it plays a sole purpose in a Transformers show. In the G1 series, he looks for the Matrix of Leadership, which is extremely powerful and can destroy any Transformer (also a fact of the Matrix of Leadership not important to Megatron is that it marks who the leader of the Autobot is). In the Unicron trilogy, in the show Cybertron, he looks for the four Cybertronian keys so that he and the Decepticons will conquer the universe. In the live-action movies and the Animated TV show (which aired on Cartoon Network), he looks for the All Spark, in both shows, the All Spark is a cube that both has information of Cybertronian history and one piece of the All Spark will bring a dead Transformer back to life.
 * In Generations 1, Megatron's primary alt mode is a pistol gun. In many later & modern versions, his alt mode has been turned into a tank or a Cybertronian jet or even a triple changer. This method also happened to his loyal follower Soundwave, who in modern versions either transforms into a jet or a van & Shockwave, who also like Megatron, transforms into a tank or oftentimes as jet or helicopter.
 * Megatron's alt mode being changed throughout the years is due to the gun ban law as his pistol mode greatly resembles an actual gun.
 * The Walther P38 (Megatron's alternate mode) was manufactured by Nazi Germany during World War II and was used by the Wehrmacht, apparently was also an inspiration for the mode of transformation of this one; Since Megatron was also inspired in Hitler when it was created.