It is universally known that the protagonist of Avatar:The Last Airbender is Aang, the eponymous Airbender out to save the world from the Fire Nation. But I believe it can also very easily be the tale of Zuko as well, from exile to acceptance, to redemption.
Can Zuko really be known as a joint protagonist with Aang and the rest of Team Avatar as a whole, or is he considered a deuteragonist (secondary protagonist)?
Case 1: He could be considered an overall protagonist because he's very nearly as important to the story as Aang is, and both come to great resolutions at the end, including the mending of a friendship (but only Zuko knows the real link) that was broken by their ancestors. Though he was an enemy at first, he joined Team Avatar, made up for his treacherous behaviour beforehand and ultimately became a joint protagonist.
Case 2: He could be considered a deuteragonist because although his character serves as a very strong foil for Aang's pacifism, he serves his own roles in the story quite well. He starts off as the main antagonist, then becomes anti-hero, then redeemed, and at the very end is rewarded for staying true to the overall goodness within him, even when tempted by dark intentions. He conflicts with Aang many times, but each time it is with more respect for the latter and his skills in combat. Maybe not at first, but eventually becomes such that he decides to change allegiances for good after the Invasion of the Fire Nation, despite a crisis of confidence between Lake Laogai and The Crossroads of Destiny.
The Wikipedia definition of a deuteragonist states that it refers to the "second actor" (prevalent especially in Greek theatre, but notwithstanding...). It also states that it is a character that could either side towards or against the protagonist at different points in the story, depending on the second protagonist's own conflicts. Never mind what it would say at the bottom of that page. It's strictly an opinion-based question.
So after all that, what do you guys think of Zuko's status during the series?