Yeah, that asshole went from bad to worse. Every other villain has some level of redemption, even if it's just understanding them enough to jive with them (cough Zenos yae Galvus cough).
I enjoy the occasional irredeemable, evil for evil's sake villain who nevertheless has a goal and the competence to carry it out. It was also cool when he
did a thing
came back from death just to scold Hermes for... let me check my notes... not being evil enough.
Valens on the other hand? Dude can burn for all I care. He was sadistic for no reason, he only wanted power at any cost, and relied on the technology and experience of others that he ultimately couldn't control. The only good thing he did was
Caim ends up thinking he saved the world, but actually doomed humans in both timelines.
Zero was stopping the weed. Not only did she have to murder her "sisters" for that, but she also kind of fucked it up, leading to the events of the first game.