1) Vaatu did not need Unalaq to act as a free agent. Vaatu was not weak or anything after he freed himself. So why did Vaatu fuse with Unalaq? It's not his nature to cooperate or share power.
2) If Raava shrinks when Vaatu grows, why didn't the opposite happen in 10,000 years? Why is Raava still small?
3) Why don't Korra and Aang have tentacles like the Dark Avatar? Or a Raava-Korra-mixed-look like the Dark Avatar?
4) How did Korra embrace Avatar State or the ultimate chakra thing without Raava in herself? She's the "avatar" of Raava. Without her, Korra is just a human. Can anyone just meditate and become a giant android energy?
This season makes me very, very sad. :(