The tale of Avatar: The Last Airbender may have been aimed at children, but it's clear that the morals ingrained in its context are universal. Nearly all of its characters, both negative and positive, exhibit aspirations that are, to some degree, plausible — ultimately turning the story into an intricate game with serious socio-political outcomes.
Each character is governed by a set of principles unique to them, so they act according to what they believe to be right (and only rarely behave out of unadulterated animosity.) There is a shocking number of betrayals that take place in ATLA, performed as much by the heroes as by the villains.
Zuko Hires An Assassin (And Then Forgets About It)
After Azula taunts Zuko about the possibility that Aang may have survived her Lightning in Ba Sing Se, he grows more and more terrified at the prospect of his father finding out.
He hires Combustion Man, a secretive but extremely dedicated assassin, to follow Team Avatar's trail (and kill Aang if he's alive.) The gang barely manages to escape from the assassin's telepathic blasts on three separate occasions, the last of which occurs regardless of Zuko's attempts to stop Combustion Man.
The Avatar Leaves His People To Die
While it can be argued that Aang is unaware of Fire Lord Sozin's plan for the Air Nomads, the fact that he abandons the Southern Air Temple (and Monk Gyatso) is a betrayal of his destiny and duty towards the world.
As the Avatar, Aang does not have the luxury of choosing his own journey, because the incredible powers he has been blessed with come with an important caveat: responsibility. When Aang rejects his role, he indirectly abandons the Air Nomads and everyone else.
Ty Lee & Mai Refuse To Follow Azula Anymore
Interestingly, this case of betrayal has a massively positive outcome since Azula loses her two closest friends — and, as a result, her mental balance — when Mai intentionally allows Zuko to escape and Ty Lee paralyzes Azula to protect Mai.
This infuriates the Fire Princess, who has both of them imprisoned for "treason." Ultimately, it is this event that helps Zuko and Katara triumph over Azula in their final battle, because she simply isn't the powerhouse she used to be.
Fire Lord Sozin Basically Kills His Best Friend
A flashback episode relates the history of Fire Lord Sozin, starting with his childhood best friend, Avatar Roku. The two boys grow up together in the Fire Nation Capital, but their lives are set on drastically different paths when the Fire Sages reveal Roku to be the Avatar.
Several decades later, Sozin spies Roku's island being engulfed by lava and rushes to help him but finally decides to let the Avatar perish in the eruption despite having the power to save him.
Aang Hides Hakoda's Location
Katara and Sokka are beside themselves with joy after discovering that their father, Chief Hakoda, is still alive and kicking. Their excitement inadvertently excludes Aang, who feels that he's going to be abandoned if his best friends choose their dad over him.
Therefore, when he is given a map leading to Hakoda's location, the Avatar hides it from Katara and Sokka, a choice that backfires on him. Luckily, the two Water Tribers understand the importance of defeating Ozai.
Zuko And Katara In Ba Sing Se
In the Crystal Catacombs, Katara and Zuko temporarily reconcile through their shared trauma — losing their mothers to the Fire Nation. Zuko goes so far as to say that he's "free to determine [his] own destiny", even if he cannot erase his scar.
In fact, Katara nearly uses her special water from the Spirit Oasis at the North Pole to heal Zuko's facial mark but is thankfully interrupted by Aang and Iroh. The so-called banished prince proceeds to betray her soon after, allowing Katara to preserve the water for Aang's fatal injury.
Aang Keeps The Truth From Wan Shi Tong
Aang (and the rest of Team Avatar) make empty promises to Wan Shi Tong, swearing that they have no intention of using the knowledge in his near-infinite Library for violence and destruction.
This would have marked the beginning of an important alliance if Aang hadn't flat-out lied, as Wan Shi Tong eventually discovers that they are after the date of the next solar eclipse in order to plan an invasion of the Fire Kingdom. Perhaps the reason the Day of Black Sun fails miserably is poetic justice.
Long Feng & The Dai Li
The Dai Li, helmed by the viciously cut-throat Long Feng, have spent years consolidating power away from the Earth Kingdom throne, performing what can only be labeled as a series of shameless betrayals.
They brainwash their own citizens into believing that "there is no war in Ba Sing Se", and go to extreme lengths to maintain this narrative, regardless of how many people are killed, jailed, or even inconvenienced.
Katara Uses Bloodbending
Katara's tutelage under the Master Waterbender Hama allows her to learn some fabulous new tricks and techniques, but she is distraught when her new mentor reveals herself to be a monster who tortures innocents in the name of ancient vengeance.
Katara employs Bloodbending to take Hama down, but only since there's no other way to save Aang and Sokka's lives. However, she redeems herself by ensuring that Bloodbending would be officially banned in the future.
Zuko Sides With Azula Over Iroh
It almost feels like the theme of Zuko's journey is betrayal, but this behavior can be attributed to his early childhood experiences, especially with his father. Zuko naturally uses deception to further his goals and remains unable to understand the magnitude of his mistakes for a very long time.
Fortunately, when he sides with Azula in Ba Sing Se, he causes Uncle Iroh incredible anguish, which gradually forces him to think beyond himself for the first time.