Here's the highlights: Mai gets bloodbent to death in broad daylight (Note that this predates Korra), which is seen as a good, heroic act the perpetrator pulls, and she is treated as the villain even though she has a point why Zuko and Katara getting together would be problematic. Zuko and Katara spend all their time wangsting and have nothing in common with their canon counterparts. Zuko beats Mai before leaving her. Toph wears pretty dresses all the time and doesn't mind that she was turned into a girly-girl with nothing in common with her former self. Sokka ends up with AZULA. Who has amnesia, turning her into a clone of Yue. During a sex scene, Aang appears to go into the Avatar State. Aang is the least useful character in the thing. Aang found a remaining tribe of Air Nomads, who he abandons. Zuko abandons the Fire Nation for four months to hang out with his girlfriend at the Bei Fong estate. Sokka and Katara are, for some reason, prince and princess of the Water Tribes now. AZULA IS A PURITY SUE, and Zuko and their mother talk about how she's so much better this way (an amnesiac, recall), implying that yes, Azula was right and her family never loved her. The one thing people actually like about it is Sho, Mai's inexplicably-existing older brother, who's cool, sexy, and trying to kill the Sue-Wraiths that were once canon characters.

Oh, and a lot of it's been traced wholesale- drawings matching up line for line with screenshots from the show levels of "traced wholesale". And full of spelling mistakes. And has nothing to do with the actual canon verse.