He's gauche, and he stumbles on his speech. His hair is unkempt, and he has a mark that adorns half his face. He's stubborn, and he's impulsive. But— he's sweet, and his intentions are pure. He's handsome, and his eyes are passionate. He's gentle, and he is honorable. He is Zuko, he is her Zuko. Katara's Zuko. And, she will take him, every inch and part of him, because that's the man she fell in love with.
He may blush every time he tries to compliment her, and it may come out all funny and staggered. He may refuse to back down from an argument for days, and blurt out something he doesn't mean without thinking. But— he kisses away her tears when she cries, and he only ever wants her happiness that is always above his own. He walks into the room making every girl's head turn, and the way his passionate, amber eyes gaze into her azure orbs is enough to make her fall for him. He always asks how she is and for permission before he makes a move, and he stands boldly; strongly ruling his nation, helping the world. He is Zuko, and she loves him, his firebending, his warmth, the heat of love and his warm-tempered body against hers.
But, most especially, Katara loves the way he sweeps her off her feet, kisses her tenderly, and mutters, "I love you," making her melt into him each and every time.