I liked the season 3 and 4 finales far better than the Season 1 and 2 ones. I if I had to rank then I would go:

1. The Last Stand

2. Venom of the Red Lotus

3. Endgame

4. Light in the Dark

Yea, seasons 1 and 2 weren't that good in my opinion

I don't care what anyone says I love light in the dark with Korra discovering that she's still powerful without raava and the spirit Korra and vaatu laser fight I really liked and the scene when Korra re merges with raava is so beautiful and the music is great.

There some about Venom of the Red Lotus that gets me everytime. the way how at the end we see mixed emotions, mostly happiness from jinora becoming a master and also sadness after seeing the state that korra is in is so incredible. like the stuff shes been through in that episode alone is mind boggling