4. Jigoku Shoujo (Hell Girl)

She may look cute, but each episode gets creepier and creepier
She may look cute, but each episode gets creepier and creepier

Be careful what you wish for, especially if you’re about to make a deal with the devil this Halloween. The anime focuses on a series of stories where unhappy individuals seek revenge on their enemies. They turn to Ai Enma, a demonic existence, who agrees to take revenge on their behalf through a website known as Hell Correspondence. However, there’s a high price to pay as both the individual making the deal and their enemies are condemned to hell as a result. While Ai Enma may seem rather adorable, her expressionless, doll-like face and the ill fate of her clients do leave a rather disturbing note after each episode. We did discover an actual hell correspondence site, though we wouldn’t recommend keying in a name at midnight.

Official site here.