“Aang, Our actions always have an effect..sometimes positive, sometimes negative…and sometimes not for many lifetimes.” - Avatar Kyoshi
-Separated Raava and Vaatu, which unleashed darkness and chaos in the world. After realizing the error of his ways, he then vows to help Raava defeat Vaatu in the Harmonic Convergence.
-It is important to note that without this mistake, the Avatar would not have existed in the first place.
-After imprisoning Vaatu in a hollow of a tree in the Spirit World, he then guided the spirits to leave the physical world and return home to the Spirit World. Wan also tried to maintain balance in the world and urged different groups of people to live in peaceful coexistence. But more wars have occurred since then and the Avatar Cycle begins as it is up to the next Avatar(s) to maintain peace and balance in the world.
-Trained the Dai Li for preserving the cultural heritage of Ba Sing Se. They later became the most corrupt elite earthbending police in the world. Aang had to deal with them and their leader Long Feng to inform the city of the hundred year war.
-Separated Kyoshi Island from the Main Land. By doing this, Chin the Conqueror fell to his death, later the town of Chin blames the Avatar for the death of their leader and created “Avatar Day”, an annual festival held to defame the Avatar in the Chin Village. Aang later had to clear the Avatar’s name and was almost boiled in oil. Later, he saved the village from the Rough Rhinos, changing the tradition of Avatar Day and putting the name of the Avatar in a positive light.
-Sparing Fire Lord Sozin’s life for the sake of their past friendship, Upon Roku’s death due to Sozin’s betrayal, Sozin was able to expand his empire and used the comet (later renamed Sozn’s Comet) to enhance the abilities of his firebender army and launched a genocidal attack on the Air Nomads in an attempt to kill Aang. These events also led to the hundred year war and the genocide of the Airbenders. Leaving Aang, to defeat Sozin’s grandson, Fire Lord Ozai before Sozin’s Comet arrives.
Avatar Aang - Disappeared for a hundred years, leaving the world to suffer in the war against the Fire Nation. But this mistake was not passed down to Korra, because he already ended the war.
- Failure to recapture Yakone as he was able to escape because of his former gang and altered his appearance and started a new life in the Northern Water Tribe. Even with his bending gone, He was still able to teach his kids bloodbending to avenge him. Yakone’s sons still became soldiers of revenge, Tarrlok became a corrupted councilman and Noatak became Amon, the leader of the anti-bending revolution. Leaving Korra, to deal with the two bloodbending brothers in Republic City.