Normally for these kinds of things, I pick some extremely silly minor character like Chong or Cabbage Man or Fire Nation Man. But honestly, it’s a tie between a bunch of characters.
Aang – Because he’s awesome. And despite Zuko always being highlighted for his struggles and his transformation throughout the show, Aang struggles and fights and transforms in a way that almost mirrors Zuko. It’s not talked about nearly as much as Zuko, but his coming to terms with his destiny, the reality of his people’s destruction, and choosing peace over violence, even when facing the most evil man on the planet all show how he, at the end of the series, is no longer just some kid wanting to goof off and get into misadventures. He matures, becomes stronger, and finds his place in the world. He transforms into The Avatar.
Toph – Because it’s freaking Toph. nuff said
Iroh – He begins as the silly old wise man accompanying our young, angry prince, but his character is so refined. He makes you laugh with his silly shenanigans, inspires with words of great wisdom, and saddens you with his own losses.
Bumi – Because everything he says puts a grin on my face that stretches from ear to ear. I absolutely love him.
This is a signature about things.