While its rough plot synopsis makes Avatar: The Last Airbender sound like a generic fantasy show, the series actually does an excellent job at subverting and re-contextualizing many overused genre tropes, specifically the idea of a "Chosen One" that was popularized by franchises like Star Wars and The Matrix.
In fact, the concept of the Avatar is already a clever subversion of the Chosen One because it brings in the idea of reincarnation. Whenever an Avatar dies, another is reincarnated into another bender, as dictated by the cyclic order of fire, air, water, and earth. For example, the Avatar before Aang was a firebender named Roku, which is why Fire Lord Sozin wiped out most of the Air Nomads and ultimately kickstarted the Hundred Year War shortly after Aang accidentally froze himself in time.
Each Avatar can also activate a defense mechanism called "the Avatar State," which allows them to access the skills and knowledge of all previous Avatars during increasingly difficult situations, but even that has limits. If an Avatar is killed while in the Avatar State, the reincarnation cycle will break and the Avatar will cease to exist. To quote Avatar Roku, "In the Avatar State, you're at your most powerful, but you are also at your most vulnerable."
