"We need more complex characters" and people can't even stand Val Velocity.
I get that he murdered Dr. D who's a fan favourite character and he is a dick to the Girl, I'm not justifying this behaviour, but this is part of his complexity.
Personally, I think his behaviour is mostly related to the situation he's living in: imagine living in a destroyed, post-apocalyptic world with your friends, where you are not sure you will find something to eat everyday or clean water; where a government is trying to exterminate your kind because decided to not conform to omologation and propaganda and where survival is unsure.
Then one of your friends get killed in front of you and you are the only atheist who doesn't believe in anything after death. Everyone else believes in afterlife, so they might be sad but still having hopes that your friend is fine now. But you? You lost your friend. No hopes. No relief.
And a young girl you never met and you don't know shows up and everyone believes she is gonna save everyone. In a realistic situation I think no one would believe something like that when your everyday priority is to survive.
TW for this part (mental health issues)
I think Val was more likely to have mental health problems than the rest of his group (Vamos, Vaya, Volume and Vynil) and the world he lives in only worsened existing problems. I personally headcanon him as BPD because of personal experiences and the whole situation just worsened it, to the point he started having bad psychosis, paranoia, etc...
Before anyone starts being annoying: NO, NOT EVERY PERSON WITH BPD OR ANY OTHER MENTAL ILLNESS IS A BAD PERSON OR A MURDERER.
Maybe if he lived in a different world, he received the help he needed, he would have been a better guy (at the end he even recognises his wrongs and apologises).
Sorry for my shitty English, but my first language is Italian.