ITA. I'm still in shock. Like Cthulhudrew said, it feels feel like they had two stories to tell, and ended up telling none. Maybe, if they had focused on the bond between Frank and Amy, it might have worked for me. They could use that relationship to bring something new and deep and transformative about the character. I mean, the whole first season was based on Frank's relationship with David Lieberman - and it worked like a charm. Here, not so much. The biggest mistake, for me, was the casting of Amy. Georgia Whigham might be a good actress, but she's too old and breezy for the part. They kept referring to her as "kid", but she didn't look like a teenager at all. She looked 22-25 to me. If they wanted a teenager, they should have cast one, and make her a little more intense - then maybe we could believe she was devastated for losing everyone she loved. Also, their relationship was too superficial. So much to explore there: can Castle justify turning a girl into a killer like himself, just to numb down some of the pain he has for losing his biological kids? Can someone without Castle's background and trauma learn to murder people in the same effective way he does? Is that a valid choice?
Anyway, not satisfied at all with this season. Watched episodes 1-6, fast forwarded through 7-10, and then watched the three final episodes, just to see how it ended. What a disappointment. I still love Jon Bernthal, still love the character, still invested in the series. Maybe we can meet again in another life/streaming channel?