A/N: A short post I wrote while watching the final two episodes of ATLA made a good short story.
That final Agni Kai…
Zuko doesn't hesitate to accept Azula's almost offhand challenge to a duel. He sees that something in his sister has cracked, that there's a strain on her mind that slowly tearing her apart.
And it seems that Azula herself knows it. She's paranoid, hallucinating, but still trying to make it through and see her ultimate goal achieved, becoming Fire Lord. Then comes her annoying older brother, the one she's always shown up and always been better than. He agrees to fight her and then the unthinkable begins to happen: Azula is losing.
She is losing to her brother and she knows it. His attacks are stronger than hers. Her desperation is growing visibly. Somehow, Zuko has surpassed her, left her in the dust.
She cannot bear this shame, this humiliation of losing to her brother.
So what does she do? How does she answer his taunt?
She cheats. She aims for the girl Zuko brought with him.
Zuko can redirect her lightning. Katara cannot.
She thinks she's won, but then her stupid brother does something so catastrophically stupid, it's unthinkable.
He sacrifices himself for a Water Tribe girl he used to hunt.
And Azula regrets nothing. She still goes after Katara, still tries to take her out. While Zuko can do nothing.
Now the fight is on Katara's turf and guess who wins.
The Water Tribe peasant.
After all that, Azula snaps. She can't take this anymore. Her ambition is crushed, she's personally humiliated, and it's over.
It's all over.