People who have watched Avatar: The Last Airbender and read their comics know that the creators truly want to focus most of the story on their two protagonists: Aang and Zuko. The characterisation of these two was the best aspect of season 1, Zuko's and Aang's character arcs are the most talked about aspect of the show, and their dynamic is one of the first things people talk about when talking about how inferior the sequel series is. Before elaborating on these, I would like to talk about two specific episodes sandwiching the introduction of Toph.
In the episode Avatar Day, Aang finds out that a village in Earth Kingdom hates him for the mistakes he made in one of his past lives (being extremely loose on the word "mistake"). Aang decides to confront the village and pay due for his crimes. When the town was attacked, Aang saved them from the bullies from fire nation. As a reward, the village hailed him as a hero.
Two episodes later, in Zuko Alone, Zuko finds a village which hates the fire nation for causing them so much suffering. Zuko hides his own past as to not face the consequences. Later, when the bullies from the earth kingdom kidnapped a child, Zuko decided to rescue him. To protect them, he was forced to use firebending and expose his identity. After Zuko defeated them, the town (including the kid who saw Zuko as a brother) turned on him and demanded he leave the town immediately.
There are a few other episodes I want to talk about, but this is a good place to start. These two episode help us understand both the episodic and seasonal arcs of these two characters. While Aang is redeemed as a hero by the village, Zuko gets to stay a villain and is kicked out. Now, a wrong interpretation here can be that the villagers who kicked Zuko out were awful people, or that Aang's story was too clichéd. Even if these two episodes were not deliberate, their placement is essentially perfect with respect to each other.
While Aang is moving forward and adding people to his entourage with Toph, Zuko is moving backwards and being more and more isolated, which started with him splitting up with Iroh. This bit of distance is what makes Iroh a necessary part of his development. The hardships he suffered without him did not help him develop as a person. Zuko ended the episode believing that he was punished for doing the right thing, when that is not the truth. Zuko was simply punished for all the pain and suffering he has inflicted in the past.
On this note, I would like to bring up Bojack Horseman. The primary lesson in the show is that your past, no matter how sad or tragic it is, will not heal the damage you have inflicted upon others, and it will forever be your responsibility. Well, Zuko is presented with even tougher dilemmas. While it is famously his honour he is seeking, he is, in fact, only seeking identity. He believes that he will gain it back if he is accepted by his father. Also, he never has to know anyone long enough to understand the consequences of his actions. These are faced by him in the arc at The Boiling Rock, whether it is meeting the girl whose village he has burnt down, getting interrogated by his girlfriend whom he abandoned through a letter, or not earning the trust of Sokka's dad (until Sokka backed him up).
Now, Aang is not seen as a complex character since Zuko's character writing completely outshines his, but that is not the case. While knowing why a villain is evil is important, knowing why a hero is so sacrificial is just as essential for good characterisation. Aang feels that he is the primary cause for letting the war start and causing a hundred years of suffering and death. He has lost all airbenders to the war, has had to see them oppress and enslave, and was continuously hunted by them. After all of this, Aang choosing to let the Fire Lord live becomes clear. Since he IS the last airbender, the only one who can pass on the values of his people, he could not let the biggest one, their pacifism, be forgotten. Every time Aang uses his skills for reasons other than self-defence or defending others, we see him being disconnected from the nomads. I still feel that the final duel between him and Ozai is underrated as fans tend to dismiss it due to the visually groundbreaking Agni Kai between Zuko and Azula.
This is a TV show I could talk about for days without running out of new ideas, interpretations and new layers of understanding. I will make many more posts about this show in the future. Every single primary and secondary character in the show is due his or her own article about their writing. No one is as happy as I am that this show is undergoing a new rennaisance. I have good hopes for the future of this franchise as it explores new characters, continues the story of the old ones, and may undergo a reboot without facing the restrictions of being a nickelodeon show.