And of course, Korra kills the Avatar Cycle.. Not sure why the writers decided to include that aspect. I mean it sets up a new age or whatever, but presumably the cycle is going to start again (with Korra as the new first Avatar), so it really doesn't feel like it was necessary. I guess it's to give the series a break from Aang, but everyone liked seeing Aang (I think?). And now she just doesn't have the wisdom of all her past lives.. I guess that could be a problem later?
On that note, it was nice seeing Tenzen finally resolve his issues with being Aang's son. I honestly was expecting Jinorra to become the new light spirit or give up her life to revive Raava, so it was a nice surprise seeing her survive.
For the most part, the battles were good, but not as good as Aang vs Ozai. IMO the best was when they returned to the real world and were battling. And then Unalaq became a giant.. I honestly could have done without the giant spirit battle seeing as it felt like it didn't add much to the battle. And for that matter, why Republic City? I guess so Varick could break out and be relevant in Books 3 and 4, but apart from that, didn't feel like it was necessary to have Unalaq attack there.
Oh, and next time harmonic convergence occurs though, doesn't that mean that Vaatu will be born from (or exist within) the Avatar, and if it escapes, then it can merge with another human to give them control of the four elements?