Zim

Invader Zim is the titular protagonist of the show of the same name.

Zim is a member of the alien Irken race. Since his actions usually lead to disaster (having nearly destroyed Irk during Operation Impending Doom I) his leaders, the Almighty Tallest, banished him to Foodcourtia. While there, however, Zim heard of Operation Impending Doom II, and - obviously not understanding the purpose of his previous exile - "quit being banished" and ventured to Conventia in the hope of getting an assignment. Chagrined, the Almighty Tallest sent him on a "secret mission" to Earth (though they did not know much of the planet at the time), in order to keep him away from Operation Impending Doom II.

After arriving on Earth, Zim enrolled in the nearest elementary skool to begin his infiltration and gather information about the indigenous race. There, he became quick rivals with Dib, an avid preteen paranormal investigator. Zim wants to conquer Earth, mostly to prove his superiority and impress his leaders. However, as mentioned by Gaz in the episode Bloaty's Pizza Hog, "he's so bad at it."

Although he is the protagonist, Zim is morally and ethically a villain (though occasionally considered an antihero), being overall a fairly unsympathetic character, though he occasionally shows some kindness towards certain characters (such as GIR in Walk of Doom), and usually only causing chaos and destruction for either himself, his own race, or Earth. His unawareness of his actions are most likely the result of being a "defect" as revealed in the cancelled episode The Trial