I think I remember when in the north pole while in the avatar states, Aang killed Admiral Jaoh Zaoh How? grrr... "Mr. I want to kill the moon because my ego is three times the size of a fire land's super blimp." (Didn't know how to spell his name. To lazy to look it up.)

Admittedly, Zuko tried to save him, but his own pride got in the way and he prefered to be dragged to the bottom of the ocean from the Aang/Ocean spirit monster that was saving the day.