Toph Mellow
I dnt think Aang is a weakling. He was just a thirteen years old kid, when he defeated Ozai. Although he is the Avatar, he had not mastered water, earth and fire fully back then. So avatar state was essential for Aang to win the fight. Otherwise it would have being bit out of belief. Every thing was perfect in "Avatar Aang". I would not have wanted it to end any other way! I agree with you, the other thing is ozai wanted to kill aang but aang didn't want to kill him. if I remember right aang could have aimed lighting back at ozai, but he didn't. I do think he mastered water though.