Today, my Amazon account suggested "Elfen Lied,” and I have to say it’s a dark manga/anime.
The story starts with Lucy, a Diclonii, escaping from a top-secret government installation. On her way out, she kills every guard who tries to stop her.
The Diclonii are human-like but have stubby horns on their heads. These horns give them the ability to telekinetically move objects around, throw people, block bullets, and open doors.
Lucy is a tortured soul with a tragic story. She started life as a happy person, but everyone around her was evil, from the parents who deserted her to the children at school who tormented her and killed her dog.
It didn’t get any better as she grew up, with the government agency torturing her and locking her up.
The Director of this lab, Dr. Kakuwazu, wants to isolate the gene that gives Diclonii their horns so he can use them as the eves in a new world where humans have been eradicated. In order to try to get his new world, he takes these innocent girls (So far, all Diclonii are female,) tortures them, rapes them, and treats them like animals.
When Lucy escapes, she loses her memory and is found by Kouta and Yuda, who take her to the place where Kouta is staying. Having no other name for her, he calls her Nyuu. Nyuu has a childlike innocence but switches back to Lucy when she’s attacked by a homicidal psycho special forces agent named Bandou. In self-defense, Lucy cuts off an arm and a leg and leaves him for dead.
This story is grimdark beyond grimdark, and it all stems from abuse and torture.
I could go on, but this is just about the first nine episodes.
I watched Elfen Lied some years back. It's good, but even as someone who likes dark and bleak stories, it's something I had to take in small doses.
Man I watched that on youtube in multiple parts per episode when I was a teen. The OP music still gets into my head every so often.