I loved the first season probably because it felt like a continuation of "Avatar: The Last Airbender". After all, in Aang's adventure we did get all the elements except Air, so it was really great to see Korra learning to master that element and grow as a person. I know there was complaints about "the ghost in the machine" finale, but I didn't mind it and I felt that there was something spiritual going on that we, the audience, did not yet understand.
Therefore, the logical next step, after the avatar is a master all four elements, would be a spiritual journey. I remember little teases of the spirit world during A:TLA and really craving more of that. It was really awesome seeing Wan and getting an understanding from the very beginning, but then all that interesting potential storyline was torn away never to return. I remember being very confused at the end of the second season, but still being interested on what changed in the world.
Four new anagonists are introduced and random people seem to gain the power to bend, but only air. Why only air? I don't remember it ever being discussed. There is an existence of a group, opposite of the White Lotus, called the Red Lotus. What was their plan? I'm not really sure. Are there still members of their group in the universe. ::Shrug.:: It feels like we got more questions than answers in the third season, and the Avatar, who doesn't really know what to do with her life, is almost killed. It definitely feels like things are way out of balance.
So, what will our avatar do to bring the world back into balance? Nothing. Not for a while it seems. She's still messed up after 2 years, I believe. There was a random soldier who took it upon herself to fix what was broken, and became power hungry in the process. Where the Fire nation took over after avatar Aang disappeared, it felt like the beginnings of that, but instead with the Earth nation, and I could appreciate that logic. At the end of the day, I guess it's ironic or may fitting that Korra destroyed the city that Aang built.