Megatron is the main antagonist in the 1984 TV show, The Transformers and the secondary antagonist of the 1986 film, The Transformers: The Movie. He is known for throwing tantrums, building giant griffins, murdering puppies or licking humans.
In the Movie
In the year 2005, Megatron learned of the Autobots' plan to stage a major strike against him, and he responded by hijacking an Autobot shuttle on its way to Earth. After wiping out the occupants of the shuttle, Megatron announced his intention to wipe out the city and cripple the Autobot war effort, then looked down to see the wounded Ironhide crawling towards him. Deeming the action "heroic nonsense", Megatron delivered a point-blank fusion cannon blast to Ironhide's head, killing him.
When the shuttle began its approach to Autobot City, the young Autobot Hot Rod was able to spot the Decepticons aboard from his vantage point on Lookout Mountain and opened fire, exposing the villains before they were actually able to penetrate Autobot City. Megatron was undeterred, and he initiated a massive siege of the armored fortress. After a night of combat, Devastator successfully breached the city walls, allowing Megatron to enter. Before Megatron could get too deeply into the city, however, Optimus Prime arrived and faced him in a final battle. Megatron fought fiercely, and although deprived of his fusion cannon, he tore into Prime with a laser sword and even hunks of rubble, threatening to rip out the Autobot leader's optics.
Ultimately, Optimus Prime prevailed, bringing Megatron to his knees and standing over him, ion blaster in hand, poised to deliver the killing blow. Spotting a discarded pistol lying nearby, Megatron stalled for time by begging for mercy, crawling ever closer to the weapon, until Hot Rod spotted what he was doing and jumped him. Hot Rod proved a much less formidable opponent for Megatron, even in his weakened state, and he seized the youth, using him as a shield while he grabbed the gun and opened fire on Prime. Prime was felled by the shots, and Megatron tossed Hot Rod aside, striding up to the fallen Prime and preparing to end their war once and for all. With his last ounce of strength, however, Prime caught Megatron off-guard with a double axe-handle blow and sent the Decepticon leader toppling over the edge of the overhang on which they were standing. Crippled by the fall, Megatron was carried to the safety of Astrotrain by Soundwave as the tide of battle turned and the Decepticons retreated. Although Megatron was defeated, he had not failed; the wounds Optimus Prime had suffered were mortal, and he died soon after.
On the journey back to Cybertron, it became necessary for the Decepticons to jettison excess mass in order to return home safely. The wounded Decepticons were voted out and set adrift in space, with Starscream taking great delight in personally jettisoning Megatron, despite Megatron's protestations that he still functioned. Before long, however, Megatron's drifting body was found by the planet-eating Unicron, who offered to rebuild the Decepticon's body if he would destroy the Autobot Matrix of Leadership for Unicron. Megatron professed that the Matrix had died with Optimus Prime, but Unicron revealed that it had been passed to the Autobots' new leader, Ultra Magnus. Testing the waters, Megatron inquired what he would receive for doing Unicron's will, and despite his dubious bargaining posture, Unicron offered to recreate his wounded body and give him new troops. Megatron demanded more but was denied, as Unicron declared that Megatron now belonged to him. This was the final straw for Megatron, who refused to be anyone's servant, so Unicron simply began to consume him. In the throes of agony, Megatron accepted the chaos-bringer's offer and was recreated as Galvatron.