Starscream is a Decepticon in the various fictional Transformers universes. He appeared in several incarnations in the related comics, animated television series, and movies. Most incarnations of the Starscream character are extremely ambitious and treacherous, but with varying degrees of strength and competence. Often, Starscream is the leader of a sub-group of Decepticon attack jets called the Seekers, and in many incarnations he is also second-in-command of the Decepticons.

He makes no secret of his ambition to overthrow Megatron as Decepticon leader. He is more intelligent than the average Decepticon, ruthless, and cruel; but, he is also a coward: He is unlikely to directly act on his ultimate ambition without, in advance, secretly getting enough fellow Decepticons to support him. He considers himself vastly superior to other Decepticons, and looks down on Megatron for being antiquated in his military strategy and tactics. Starscream believes that the Decepticons should rely more on guile and speed rather than brute destructive force to defeat the Autobots; although, even when Starscream is given the chance to strike out on his own, he is rarely more successful than Megatron -- often, considerably less. Megatron overlooks the potential threat that Starscream represents because he believes that Starscream is very good at his job. However, Starscream often exhausts Megatron's patience quickly; violent-yet-brief verbal and/or physical conflicts are not uncommon between the two. Usually, these result in Megatron treating Starscream in a humiliatingly dismissive manner.

Starscream's ghost also appeared for a few episodes in Beast Wars, and he eventually possessed Waspinator's body for quite some time.

(Source: Wikipedia)