Just to pitch an avatar the last airbender: what if? style series:
Aang doesn't run away and in a match with a firenation soldier, he dies while protecting the other children. Cue a scene of the firelord Sozin burning the soldier who killed him, because the order was Capture the avatar, do not kill him.
In the southern watertribe Korra is born, and while the cycle wasn't cut, it was shorter and the energy causes Korra's mother to die.
When she turns 10 years old, she accidently burns her best friend, finding out she's the avatar, but instead of being confident and starting to train, she is kept just as a waterbender. The only people who know is her, her friend, her father, the tribe chief.
She gets excesive watertribe training, while the war is soaring outside. The plot of the series start when she is 15 and finishes her waterbending training. However, her father doesn't want her to leave because he saw the dangers of what war brings.
A big fight breaks out ending in Korra running away to start her training journey firstly accompanied by her friend who she burned.
First book - earth: Korra travels trough earth kingdom and it's very focused on war, Korra finding out how bad it is, feeling huge guilt because she didn't start doing anything yet. She ends up on the Kyoshi island, who took in a young girl who lost her arm because of the firebenders. She is a very skilled earthbender though, and in Korra kinda big first act of "avatarness", she gives her back hope to start bending again.
Second book - air: An issue she is facing now is that 1. it is believed that all airbenders were killed and 2. people from the fire nation are considered enemies. With her two friends she decides that the best course of action would be trying to talk with a previous avatar, but she doesn't know about Aang and so her best bets are the previous ones. After more aimless travelling and earth training, she hears a story about a sheltered village rumored to have a big old avatar temple. Unfortunately, they don't let outsiders in. Stuff goes down and eventually, Korra explains that she needs to go inside to try to contact the avatar about airbending. They send her away, but then during the night, a child sneaks out and tells them information- a way to sneak inside the temple, and the reason they are sheltered: A family of airbenders are hiding inside. Cue them sneaking in, getting caught, and Korra getting trained in airbending.
Third book - fire: From the airbender she also finds out that the firenation have been attacking northern watertribe, but they haven't been successfull yet. During the story, Korra also mirrors Aang in struggling to be stable in avatar state. She decides to go to the northern pole to fight firenation headon even with no firebending. During the midseason finale, she gets caught by none other but young Iroh. In the cell they end up talking and it's Korra to shake his beliefs. She manages to run away without his help though, but when sthe times gets rough, it's Iroh who helps in the last strech. During that fight Korra firebends again.
Finale: Korra is again in the northern southern tribe finding out the firelord himself wants to seize the island. In a state of panic, she goes to the water spirits. In there, saying outloud that she is scared, she ends up connecting with none other than Aang. He tells her about what went down and tells her that hope is never lost. Korra then decides to try waterbending techniques on firebending- WOWOWO it works, Korra wins, season one ends with Korra not being a trained firebender but being an waterbender, airbender and an earthbender. The war isn't over, but she defetaed the firelord once, she can do it again. And if she has to, she will do it again and again and again.
