Catharsis
The Firelord stood with his back to the far wall of the throne room. He knew he was beaten. The Avatar, the two Water Tribe peasants and the blind earthbender had him cornered, and could deliver the final blow any second he chose.
"Do it," hissed Ozai.
"Not just yet," came a familiar voice, as someone stepped out of the shadows. Prince Zuko.
"So you've come back have you? I'm afraid you've come a bit late to beg for forgiveness," he said, with an air of cruel amusement in his voice.
"No, father. I don't need your forgiveness."
"Then what, you filthy traitor? You're too late to share the glory of defeating me if that is what you're after."
"The glory of slaying you is not mine to take. I've come to ask you a question." Ozai wrinkled his nose in disdain. "What's my favorite color?"
"What kind of a question is that, you traitorous worm? You disgust me." Zuko looked at his father and continued on, his fists trembling with pent up rage and anguish.
"What was my favorite childhood possession? What did I always give you for Father's day? What was my first word?" His voice began to shake, his good eye brimming with tears he refused to let fall. "Do you know? Answer me! What's my birthday, for Agni's sake! Do you even care? Did you ever care? LOOK AT ME, DAMNIT!" Ozai stood shocked for a second before answering in a voice filled with cruel, sadistic pleasure.
"No. I don't know. And I don't care. You were weak as a child and you remain weak to this day. You're a disgrace you your family and the Fire Nation, and an enemy of every other nation. Who could ever care for a pathetic thing like you? I should never have let your mother talk me into sparing you, and I should have done more than simply burn you at that Agni Kai. You chased the Avatar for two years, and end up joining him instead. You disgusting failure. You deserve to die a death worthy of a traitor of the filthiest kind." Ozai gleefully searched his son's features for the signs of pain he knew he must have caused. But the look on Zuko's face was not one of rage or grief. In fact, his face revealed no emotion at all, except for a single track of wetness through the soot and dried blood on the unblemished side of his face.
"Very well then. That is all I needed to know," he said, turning towards the Avatar and his companions, his voice sounding oddly hollow. "Aang, I believe it's time to fulfill your destiny. Finish him." From a hilt on his belt, Zuko drew a small knife and handed it to the Avatar, whose eyes filled with a sudden, painful understanding. Inscribed into the blade of the knife were the words Never give up without a fight. Aang plunged it through Lord Ozai's heart. Watching the Firelord's body fall to the ground, the dam Zuko had been keeping within his heart shattered. Zuko dropped to his knees, and all the rage and shame and sadness he had let build up inside him was finally set free. For the first time in three long years, no longer caring who saw him, Prince Zuko of the Fire Nation broke down and cried.