Searching for the Darkest shows I can find!

So as the title says I'm looking for animes with either overall extremely dark storylines or their is a part of the story that is just extremely dark. Not looking for horror explicitly, but not against it either. I've watched almost all the basic answers that could be given so I'm looking for ones that maybe I haven't heard of. A basic list of what I have watched and enjoyed goes as follows; Another, Shiki, Black Lagoon, Elfen Leid, and plenty others. Even if you recommend me something I've watched it would be appreciated for the effort. Currently I've been binging the when they cry series old gen before I watch the new series. (Yes I've played the games haha. ) but anything as dark as any of the when they cry series kinda what I'm looking for. Appreciate you guys in advance!