While I think you make some very good points, I don't necessarily agree with them. With Amon, he was still just a child when he left home. By the time we see him in Republic City, he's in his forties. That's at least thirty years between the time he suffered abuse at his father's hands and the time he sets his plans into motion. I don't know about you, but I've never met anyone who internalized their abuse so much that they made sure their entire adult lives revolved around it. I can understand there still being bitterness, but after thirty years, it feels less like a legitimate purpose and more like he's just being a drama-queen. That is why the "big reveal" was so disappointing for me though I really liked how his end came. It was darker than anything A:TLA had done up to that point, and it was actually really beautiful from a writing standpoint.

The thing about Unalaq is that I could have respected his powers of manipulation if they hadn't been so transparent from the viewing perspective. Both the writing and the scenery set-up was so blatantly obvious that I wasn't surprised by anything they revealed about him. He was also very one-dimensional. Amon and the Red Lotus (except for Ming Hua) had facets to them that gave them character depth. I didn't get anything like that from Unalaq or Vaatu. They just were what they were, and they didn't have any room for growth as characters which is always a bit disappointing to me.

I think with the Red Lotus, you have this idea that they could only be one way. Their goal was to bring down centralized government and allow a stronger system to emerge from the chaos. Zaheer had spiritual inclinations, but that doesn't mean that everyone else had to have them. It was clear to me that the other four just cared about the goal and not necessarily Zaheer's reasoning. In order to really value and want to achieve the goal, there's no reason why any of them had to have spiritual inclinations. There isn't only one way to start rebellions or one reason to want to do so. 

Everyone can have their own reasons and purposes, and I thought that actually added a lot of depth to the group as a whole even if we never fully learn why Ghazan and Ming Hua are so loyal to the goal. P'li wanted to bring down governments because rulers essentially used her as a weapon of destruction, and she would have followed Zaheer anywhere because of their love for one another. Zaheer wanted to do it because of his spiritual beliefs. It's obvious to me that Ghazan at least believed in the end-game, and Ming Hua was probably just a psychopath who liked hurting people though that might just be a result of her mind cracking due to the terrible prison environment she was forced to be in for over a decade. To me, hers was the worst of all of them even if all of them were their own, unique forms of inhumane torture.