^ I like S1 the best, as well. The character development was the best in that book, I believe. We saw Korra go from being cocky and hotheaded to learning the meaning of patience and discipline. In book two she displayed some of those traits but did get aggressive when needed, but in book three I feel like she was more like she was at the beginning of the show, always finding something to yell about. And not just Korra, but every character showed personal growth in book one, whereas some characters felt stagnant in book three. I feel like Asami could be a much better character (and get a lot more action/be a bigger part of the team), but they didn't really have her do much in book three, I felt.
I'm still confused regarding something. At the end of book 2, it was said that Korra's connection with her past lives was severed due to her fight with Vaatu. Prior to that, we saw her use the Avatar State somewhat frequently, even at will, like when she uses it in her race with Jinora and the kids. My memory is a little fuzzy but I believe she only used it twice in book three, whereas she used it 17 times (just looked it up) between books one and two. Does the severing of her past lives also weaken her ability to use it at will, or make it less potent or something? There were a few moments in book three when I was just waiting for her to use it but she never did.
I feel that maybe the writers don't want her to use it too much because they don't want to rely it on as a crutch (its basically going Super Saiyan), but at the same time I would rather see her use it and kick some ass instead of her getting beat and Jinora coming in to save the day all the time.