Zuko was (in the beginning) the main antagonist of the show Avatar: The Last Airbender.
Zuko then joined Aang and the gang who later defeated his brother ans sister.
Zuko then moved up from the ranks of banished Prince of the Fire Nation, to Fire Lord.
At first, he was like someone else we know, a Prince of a fallen nation. General Iroh (Zuko's uncle) allowed a persistent, thirteen-year-old Zuko into a war council with Ozai and some of his generals. He ignored Iroh's instructions not to speak during the meeting when one general outlined a plan to sacrifice an entire division of new recruits in a diversionary maneuver. He fiercely disagreed with this, seeing it as a betrayal of the recruits' patriotism. The insubordinate outburst was seen as a grave insult and Ozai demanded that he participate in an Agni Kai. He agreed, unaware he would face his father, not the general he insulted. Upon turning to face his opponent, he was immediately penitent and knelt, refusing to fight, and tearfully begged for his father's forgiveness. Ozai declared his refusal a sign of cowardice and another display of disrespect, affirming that "he will learn respect, and suffering will be his teacher." Ozai burned Zuko (permanently scarring the left side of his face), stripped him of his birthright, and exiled him from his beloved homeland, declaring that he could only return if he was able to find and capture the Avatar, who disappeared one hundred years before. It was a fool's errand by all accounts (because if the Avatar had disappeared, there would be no point in searching for him), but Zuko clung onto desperately as his only hope of regaining his honor and everything he had lost.