All Hail Megatron

Background
Rebuilt by the Constructicons exactly as they had first made him countless aeons ago, Galvatron's mind was transferred (or was it copied?) into a blank laser core by Hook, using the unique subatomic perfection of the Ruby Heart of Krithella IV. Freed of the taint of Unicron, Galvatron reclaimed his rightful name and seems to have been restored in mind as well as body. He has pledged never to give up his troops to the madness of Galvatron again.

Pros

 * Is not Galvatron.
 * Is surprisingly forgiving of people who try to overthrow him, as Starscream, Blitzwing, Shockwave, Astrotrain and several others can attest. Well, maybe not Starscream.
 * Actually did put down Optimus Prime for good. Also (some personally, some indirectly) Prowl, Ironhide, Brawn, Wheeljack, Ratchet and some other dudes.
 * You can shoot him at Autobots!
 * Conquered the Smithsonian, proving that even higher learning can be defeated.
 * Is the Slag-Maker.
 * Asked Sixshot to kill Autobots, rather than his rival.
 * Is backed by the Constructicons. Devastator > Deluxe Insecticons
 * The classic look is always in.
 * You have a better chance of dying to the Autobots than to him.
 * Returned the Decepticons to prominence after Straxus' reign.
 * His toy has been rereleased in new versions about a million times.
 * Is sometimes voiced by Hugo Weaving!

Cons

 * Might actually kind of be Galvatron.
 * Skywarp, Thundercracker, and the Insecticons are still dead, so he obviously can't fix everything.
 * May not actually be as tough as Rodimus Prime.
 * Can link up to a black hole and project antimatter from another dimension into ours. This seems like it would be a good thing but when you think about it, it really isn't.
 * Might not be the Real Deal.
 * Has a trigger for a crotch.
 * Inexplicably refuses to kill blatantly obvious traitors, even when they ruin everything.
 * Is never voiced by Leonard Nimoy.
 * Fell asleep for four million years and let Shockwave wage the war. Shockwave's idea of waging war is to turn everybody off and do nothing for four million years.
 * Built a giant blue Gryphon
 * Wants to marry Nightbird (some say)

Background
Betrayed by the Constructicons or an unknown foe, Galvatron's mind stayed in his humanized body which was frozen and sent to Sunlab-2. When the humanizing process was reversed, Galvatron's body was returned to him as well. But he was terribly injured from the punishment dealt out by the Azreal, and was forced to wait in secret, biding his time and building his army. Now, he has returned and all hell follows in his stead.

Pros

 * Is Galvatron
 * The last person who tried to overthrow him is now a head on a stick
 * Risked his life during the first battle with Megatron to take down Rodimus Prime
 * Was built by Unicron
 * Megatron's a dip
 * Is ruthless and doesn't know the meaning of the word 'mercy'. It is torn from all the dictionaries in the Decepticon Empire
 * Disposed of Starscream
 * Backed by the Deluxxxe Insecticons
 * Knows the true purpose of the Sweeps

Cons

 * Is Galvatron
 * Ordered the sabotage of the New Crystal City spaceport
 * You have a better chance of dying to him than the Autobots