Dangan Ronpa is already dark, but Doubt Academy takes it even further thanks to a few key differences. Unlike in canon, where convicting the wrong person equals Game Over, here Monobear simply tells them they got it wrong before executing the innocent scapegoat. This creates a Kangaroo Court atmosphere where classmates have already lynched someone they knew was innocent to keep them from taking revenge and others have offered themselves up as Senseless Sacrifices to keep their friends from suffering the same fate.
The Insane Cafe RP trilogy has elements of this. The first was a nonsensical, hilarious and downright Narmy. The second was more plot driven and a terrorist attack on a remote laboratory was a key plot point. The 3rd installment features several assassination attempts, a few sex scenes and an impending war. Oh yeah, profanities are uttered the second and third installments.
While most of the campaigns in the Global Guardians PBEM Universe were standard Bronze Age fare, the Night Life In The Big Easy campaign, which featured a solo 1980s-style vigilante facing off against a voodoo-themed criminal empire that had been built on drugs, prostitution, and white slavery, was straight out of the Dark Age.
Welcome To Beacon and its sequel Welcome To Beacon Ultimate are considerably darker than canon RWBY. The Grimm are a more considerable threat, and the students have to face two major criminal organizations, who have no qualms causing deaths and grevious harm to the student body. Several characters also carry scars, both physical and mental, from prior encounters with the Grimm, and sex between them have been implied several times. There's a reason several players call it "RWBY as written by Gen Urobuchi"