Avatar: The Last Airbender: 3x21
Chapter Twenty-One: 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.
3 - 1Chapter One: The Awakening Sep. 21, 2007
3 - 2Chapter Two: The Headband Sep. 28, 2007
3 - 3Chapter Three: The Painted Lady Oct. 05, 2007
3 - 4Chapter Four: Sokka's Master Oct. 12, 2007
3 - 5Chapter Five: The Beach Oct. 19, 2007
3 - 6Chapter Six: The Avatar and the Fire Lord Oct. 26, 2007
3 - 7Chapter Seven: The Runaway Nov. 02, 2007
3 - 8Chapter Eight: The Puppetmaster Nov. 09, 2007
3 - 9Chapter Nine: Nightmares and Daydreams Nov. 16, 2007
3 - 10Chapter Ten: The Day of Black Sun, Part 1: The Invasion Nov. 30, 2007
3 - 11
3 - 12Chapter Twelve: The Western Air Temple Jul. 14, 2008
3 - 13Chapter Thirteen: The Firebending Masters Jul. 15, 2008
3 - 14Chapter Fourteen: The Boiling Rock, Part 1 Jul. 16, 2008
3 - 15Chapter Fifteen: The Boiling Rock, Part 2 Jul. 16, 2008
3 - 16Chapter Sixteen: The Southern Raiders Jul. 17, 2008
3 - 17Chapter Seventeen: The Ember Island Players Jul. 18, 2008
3 - 18
3 - 19Chapter Nineteen: Sozin's Comet, Part 2: The Old Masters Jul. 19, 2008
3 - 20Chapter Twenty: Sozin's Comet, Part 3: Into the Inferno Jul. 19, 2008
3 - 21Chapter Twenty-One: Sozin's Comet, Part 4: Avatar Aang Jul. 19, 2008