Canon History

...it's Starscream. He's a horrible traitorous bitch, has been, and ever will be. He's a universal constant that way. He actually led the Decepticons in Megatron's absence, which everyone seems to have blocked out of their minds. (Probably for good reason.) He will never forget this.

Cracktran History

Oh, the life of being one of three Decepticons not stuck in the bottom of a trench! What glorious days of taunting Megatron, extorting Blackout, and falling asleep at fifty thousand feet over the Atlantic because you're a moron and think that you can go without recharge for four days in a row!

Such was the wonderful existence of Starscream. Then Thundercracker, Skywarp, Frenzy, Barricade, and probably some other people all worked together to get Megatron out of the trench. Sigh.

Restored more or less to the state of being the perpetual second in command (but future leader and don't you forget it!!), Starscream has thus far had screaming arguments with his ex, Skyfire, screamingly hot makeup sex, and has and has taken over half of Skyfire's quarters. The sparkly sign is courtesy Fireflight.

Recently, he's learned that his spark (mutant immortal thing that it is) is the Decepticon Matrix. Which won't work unless it's taken out of his chest. For somewhat obvious reasons, he is not wildly eager for this to happen, and has told Unicron to go screw himself more than once, with predictable results.

He's still chased around the base by Megatron every Tuesday, to the accompaniment of cannonfire and "I'M SO SORRY I DIDN'T MEAN IT MEGATRON I'M SORRY," though he seems to have cut down on the threats to take over the Decepticons. Having three different factions, all of whom generally leap to it when any of the leaders says 'jump,' sort of confuses him.

He totally still is, though. Just you watch him.