Although the Avatar TV shows are considered Western animation, Avatar and most Western animated shows are actually animated in Korea to save money. Which is why there is a bit of credibility to this:
This is what appears to be an unfinished linetest for a scene from Avatar: Legend of Korra. In the scene, what looks to be Korra is fighting various other people with Martial Arts.
The fact that the whole video is from a Korean blog, and the animation being very similiar in style to Avatar: The Last Airbender, it makes the chances of this being real a bit higher.
As it was apprently removed from the blog, meaning it's real, let's have a look at it in Youtube form.
Please stay civil. You should not harass other users or their views.