Jet

Jet is a teenage rogue who serves as an anti-villain in Avatar: The Last Airbender. His major motivation is a xenophobic hatred of the denizens of the Fire Nation, who stems from a tragedy in his childhood, when the Fire Nation burned down his home and killed his parents.

Jet first appeared in the episode of the same name where Aang and his friends meet him and his Freedom Fighters. Katara falls head over heels in love with him. He befriends the gang and later tricks Aang and Katara of waterbending the geysers into the reservoir and flooding a town, in order to kill the Fire Nation soldiers and the innocent people in the village, under the pretense of extinguishing a forest fire. After this, he had paranoia that the Nation was trying to assasinate him and he wanted to destroy the village and "free it." He would have succeeded if Sokka had not warned everyone to evacuate the village on time. When Aang and Katara learn the truth, they fight and defeat him, leaving him frozen to a tree.

He later reappears in the Season 2 with his two closest friends from the Freedom Fighters, having understood his errors, as he travels to Ba Sing Se, the capital of the Earth Kingdom. He meets Zuko and his uncle Iroh as the two are refugees, and attempts to recruit the disowned prince in his gang but not to avail. Quickly after, he discovers that the two of them are Firebenders and his hatred gets once again the best of him. He challenges Zuko in a fight and tries to force him to firebend, so that he and his uncle would be arrested, but Zuko defeats him using only his sword and Jet is arrested by the Dai Li, the (corrupt) police of the Earth Kingdom.

In the episode "Lake Laogai" Long Feng, the head of the Dai Li, brainwashes Jet and forces him to fight against Aang and his friends. Aang manages to bring Jet back to his senses and he challenges Long Feng, both to protect the escape of Aang and his friends and to get his revenge, but the villain easily defeats him with his powerful Earthbending, leaving him grievously wounded. Jet's death was heavily implied but his ultimate fate remained unclear until the creators confirmed it.