It's only on Nebula, and not youtube yet, but The Closer Look has a great video on writing characters that people will care about and will want to follow. Hopefully, it will be up on youtube soon. I watched it on Nebula today and it made something clear about what it is that makes CD Call's character writing so dull. At least for me.
Of the four principles listed in the video, the only one I think CD's characters come close to fitting is wish fulfillment. They aren't likable. Most are actually horrible people. There is no intrigue about them, or if there is, it's not resolved. They don't invoke any empathy in me, like, ever. Living vicariously through them is about all that's left.
Except for, I don't want to do the things they do. I don't think most people want to go around slaughtering large groups of people on a whim and ignoring issues until they affect me personally and I don't think most people secretly want to cuddle with their siblings to the point outsiders think they are having sex. Even if you somehow don't see those things are strange or wrong, I still don't think they are popular fantasies.
If your sibling is hurt in a battle, I can understand feeling that you want to kill those responsible for it, especially if you actually have the power to do so. But, as a writer, you have to do something more with that. Have them struggle with it, at the very least. If you don't have them stop themselves, then have them dealing with the guilt afterwards. Hell, even if there is no guilt, have them deal with the societal ramifications.
"Killed the fascist leader of this territory. Not because he was a fascist, that's the people's fault somehow. But he forgot to say 'bless you' after my sister sneezed."
Well, now there is a power vacuum. Have your hero have to deal with that, then. At least, do that much. Have them do something. Something consistently that we can get behind. Again, that we can get behind. Slaughtering slavers, good. Randomly slaughtering someone on the street because their business deals with a business that once dealt with the slavers, but not dealing with the societal issues propping up slavers, not so good.
The video mentions Jack Reacher. A character so unlikable even the author wasn't sure people would enjoy his story. But Jack has one habit that most people can live vicariously through. Jack always, always stands up to bullies. If there is a pompous, entitled, asshole in the room, Jack IS going to punch him.
And we, as readers/watchers can get behind that.
Avatar Niva, CD's most boring character, in my opinion, doesn't have something like that. The closest she comes is she hates being the avatar, and I can almost get behind that. I think I would to...but not with the way Niva is presented as the avatar. I mean, if I didn't have to do anything about anything I didn't want to and still got to be all powerful, I probably wouldn't hate it. I might not love it, I might be done with it, but I wouldn't hate it. So, I would have no reason to act the way she does about it. She hates it, but is never faced with having to do the things she hates it for, except when it serves herself. You can't have her hate the pressure of being the avatar and then not show her suffering under that pressure.
Niva probably bothers me the most because, honestly, she's just a badly written version of Batman. They don't want to be who they are, really, but have to be. It gives him self-loathing and makes her indifferent (and leads to even more co-dependence with her sibling.) They tend to focus only on the danger in front of them and not the societal reasons for those dangers. He could do more through his wealth to change things, she could use her status the same way. Given the right circumstances; him resources and time, her training and technique, they can defeat pretty much anything. There is only a small handful of people they trust at all and only one or two they dare to be close with. No comment on this, it's a common enough trope.
But there is nuance to Batman. He has virtues that sometimes cause him pain. He doesn't kill his foes, so they return and are nearly always worse for him and the city. He's smart, he's occasionally funny in a deadpan way and he is both flawed and capable. As Bruce Wayne he's charming and caring and likable. He's empathetic, even to his enemies, even when that may bite him in the ass. And when his actions cause problems, he has to face them and deal with them.
And yes, given time and money and training, I also would like to drive around in a cool car, wearing a cool costume, seeking justice and telling people:
"I am vengeance. I am the night. I am Batman!"
And be voiced by Kevin Conroy (RIP, King)