Megatron is known as the Lord of the Decepticons, and is always trying to be replaced by Starscream, his 2nd in command.
During the war, Starscream, and the Combaticons had captured Optimus Prime and bought him before Megatron. In front of him, he executed 2 Autobot Soldiers and was ready to execute Optimus as well. But Optimus was saved as Metroplex had came online, even after being blasted by a Warp Cannon. Megatron told his men no to run, but to stand and fight the beast. All thought he was foolish to stand and fight the Titan of the Autobots, as he crushed Megatron down into the ground once, but Megatron blasted at him still, so was crushed again. But Megatron was relentless and continued to shoot at Metroplex and was crushed again, eventually was offline. Starscream named himself as new leader of the Decepticons after, but Soundwave, Shockwave, the Combaticons, and other loyalist to Megatron wouldn't accept it.
Later, after the Combaticons were arrested for disobeying Starscream's order to retreat from securing an Autobot Convoy, but destroyed it, and half its Energon supply. Meanwhile, Soundwave continued a secret project of rebuilding Megatron. After finished, Megatron left the lab and headed out for Starscream's "coronation. Starscream was defeated and exiled from the Decepticon Forces.
Megatron then, had an attack on Iacon launched, to find Tyrpticon, a beast with the skill of Metroplex, who was destroyed. Megatron told Tyrpticon that he failed him and the Decepticons, and for Soundwave to convert Tyrpticon into the Decepticon Ship, Nemesis.
Megatron's spark was extinguished during the Neo era on Cybertron, and the rank was given to Ransack