I will review all seasons:

Season 1: In the traditional child hero story, either the stakes are relatively small or the hero grows up during the story. The series opens with a two-parter, "The Boy In The Iceberg" and "The Avatar Returns". Each episode of the series has a short introductory segment that provides some background for novices. For adult viewers, this 100-year-war is a little problematic because it doesn't make much sense. Katara is a novice waterbender, and her brother Sokka appears to be a terrible navigator. We also meet Prince Zuko of the Fire Nation, who is on a quest to find the Avatar.

Season 2: Season 2 adds to the cast while also delving deeper into the characters. This is especially true in the case of Iroh and Zuko, who have a touching past involving Iroh's late son. With uncertainties regarding Zuko's objectives and a suspenseful final episode, the series comes to a close.

Season 3: "The Book of Fire," holds the darkest chapters, including the imprisonment and torture of a major character. Life in America looks and feels a lot like life in the Fire Nation as Aang, Katara, Sokka, Toph, and eventually Zuko experience it.