Kingdoms of Ruin is so dark that it comes close to flipping over into parody (I mean, even before you hit the sex-bot episode). Nastiest thing I’ve seen since Magical Girl Raising Project. Don’t get attached to any of the side characters, because their survival rate is extremely low. Also, if I recall correctly, the female lead is pretty much a cardboard cutout of a saint. And the anime ends without completing the story, and I doubt that there’s going to be another season.

So I’d maybe put that one down at the end of your priority list. If you want something darkish and violent, maybe seek out Dorehedoro instead (second season just ended, third will probably be along in a year or two).