Well the finale for ATLA was really action packed. While LoK season 3 has lots of immense, power-packed fight scenes, what makes the ATLA finale stand out is that its fight scenes emphasized each move. Not saying LoK didn’t do that, nor am I saying ATLA is better than LoK. Also, during the ATLA finale, we saw a bunch of creativity with the bending moves that we didn’t see before. For example, Aang blowing fire in a five-pointed star, Aang invincible air shield, Katara freezing and thawing herself in water, etc. Also, the comet made everything ten times more intense. You see firebenders getting so much power that they leave destruction at their wake.
That leads me to talk about Zuko and Azula’s fight, which was power-packed indeed. The soundtrack during the fight made you really connect with it too. It’s a huge brother-sister struggle. I’m stopping here because I’m hoping someone might reply or add on to what I’m going off of.