I'm not the GM or co-GM and I haven't actually gotten my character signed up, but I think I can help explain why these characters don't seem acceptable.

They are ridiculously over-the-top dark. Seriously, what do you honestly expect to happen when, tonally(at least from what I've seen) this is supposed to not be too far off from the Teen Titans cartoon. Which had a brain in a jar and a talking Gorilla as some of the final villains. I mean, they were serious and it's been ages but I remember it being a really cool arc, but they were still a brain in a jar and a talking Gorilla. Not "organ thief druglord who murdered his own parents for basically no reason aside from evil crazy and who imprisoning will somehow just make things worse". This isn't some super-dark, gritty, "realistic but not really" RP.

As for the "hero", he's flat-out too dark as well, and he has very poorly-defined powers that you haven't really defined after being directly asked about them.

... I'm sorry I'm going off like this when I'm not even a GM but it was really bothering me that you don't seem to get why they're not acceptable when it's pretty obvious to me as well.

I'm sorry if I came off as rude or something and you don't really have to listen to me but I'm pretty sure those are the reasons you're being declined.