Light in the Dark

Mmm, I could do without her avatar qualities to be honest, though her design is nice, and not too overdone.

She seems fine as only a firebender, only the avatar can bend all four elements as you know, unless shes 3 generations from Aang, or 2 from Korra, then she doesn't fit in any other timeline realistically in a non-sueish way, or shes an earth bender rather then a fire bender, or something like that, but again you'd have to go generations ahead, or generations behind, but she seems to be in Aangs time period, so you would have to change her clothing design at the least.

Also the whole 'She turned out stronger then expected' thing seems too on the sueish side. In order to give, you must take. She needs some sort of flaw to allow her to have strong capabilities, and the whole avatar system is too old and spiritual for me to believe it would get 'flawed' and create something like her. Unless you have a realistic story somewhere to support your ideas, I don't see it as realistic in the fandom. Its veering too much towards sue.

And even so, Korra is probably stronger then some might expect, but if you look at her shes realistic, she has the flaw of not a lot of self control, and impatience. Though if you follow by those guidelines, its like making a firebending Korra, so you have to watch out for that. Think of creative ways to make her flawed, and think about it. Don't just slap something unimportant like "Oh, shes not good at... math." because thats just a way to get out of it, and perhaps math isn't something important in her life, so you should make it count.

Overall I think the drawing itself is great, love the fire affects and everything but the character itself needs some working on. Its all with trial and error though.