Azula

Azula is Zuko's younger sister. A Firebending master, Azula is forced to put up with Fyre and her friends on a regular basis.

TV Show Vs. FGTC
In the TV show, Azula acts very calm and collected (until Sozin's Comet, when she went insane, but we shall overlook that). However in FGTC, Azula is often easily angered and acts nicer to soe characters than she did in the TV show. As for the other characters, she fries them.