What's the darkest anime/manga you have seen?

I can start us off. For me, it would definitely have to be Wolf's Rain. Wolfs Rain

The setting is so bleak it makes watching it pretty sad. It's a testament to the mood the anime that was going for that, years ago, there was a period when I was sad, thus just listened to Wolf's Rain music. But as dark as it was, there was at least a bit of hope that things would turn out well. The final episodes, though, are so depressively dark that it really hurt the show for me. There's a reason why the OVA has a lower score than the show for me. Whether the series it's well-made or not, I can't say, and I won't find out because the show is so depressing that I'll never watch it again.

Wolfs Rain OVA

Arigatou
I mean, the sinopsis says it all, I think: A depressing story about how a Japanese family's life goes wrong: an immoral protagonist, her sister who was gang raped before, her alcoholic mother who later devoted her life to a cult, and her father who lost favor with his company...

Reiraku
I'm sure someone is about to post Oyasumi Punpun in this thread and that is a pretty dark manga, since it's an exploration of depression, but somehow Asano made Reiraku feel even more bleak.

Dai Dark

This manga is very Dark.

[Removed]

Probably this
Magical Girl Raising Project

It wasn't very good. Edgy for the sake of being edgy.

Edit: or this
The Fruit of Grisaia

Berserk
Monster
There are more but these two are my absolute favorite

Ibitsu the manga
Ibitsu

emergence

Manga
Berserk
Uzumaki
@MasterCrash predicted this one
Oyasumi Punpun

Anime
Hotaru no Haka
Perfect Blue
Kenpuu Denki Berserk
Serial Experiments Lain

If by dark you mean depressing and hopeless, definitely Bokurano.

The thread "What is the darkest anime you can think of?" and it's comments have been merged into this thread.

You can view the merged thread's body below:

I believe this might be the darkest, even the theme is dark.
Texhnolyze

Darker than BLACK Kuro no Keiyakusha

Pick one

Shinsekai yori

Ergo Proxy

Serial Experiments Lain

Can't go wrong with this mind fucking shit
Monster

Banana Fish definitely ranks up top, but Shinsekai Yori is a close second.
BANANA FISH
Shinsekai yori

When They Cry

[Removed]

Now and Then Here and There

[Removed]

Shiki.

Perfect Blue

It's like one of those psychological horror films

Ehem..
Cossette no Shouzou
achu...
Kikoushi Enma
Basilisk Kouga Ninpouchou
Blue Gender
Memories
JinRoh

I can continue for days most of what I watch is "machure" and gritty.

Serial Experiments Lain

(note that i don't actually recommend watching this)
Pupa

I guess no one has seen this

Midori Shoujo Tsubaki

Pupa

Serial Experiments Lain
(Lain was top something for psychological genre but it was a bore for me)
School Days
Denpa Teki na Kanojo
Mahou Shoujo Site

Girls Last Tour
Kizumonogatari Part 3 Reiketsu
Samurai X Trust and Betrayal
the Garden of sinners Chapter 5 Paradox Paradigm
the Garden of sinners Chapter 7 not nothing heart Murder Speculation Part B
Shiki

Higurashi no Naku Koro ni
Mirai Nikki TV
Happy Sugar Life

Going with "I lost all hope for the world while watching it or after finishing it" as the definition of "dark":

The winner by an insurmountable margin:From the New World
Runner-up: Ringing Bell