Avatar: The Last Airbender 3x21
Sozin's Comet, Part 4: Avatar Aang
Aang defeats the Fire Lord by bending the elements within the Fire Lord and removing his fire bending abilities. After Zuko is taken down protecting Katara from Azula, Katara fights and manages to restrain Azula. Afterwards, Zuko is crowned Fire Lord and promises a better future for the world. Aang takes his place as the next Avatar, changing his attire in the process. Katara finally shows her love for Aang as they kiss in the last scene.