Some Sunny Day addon

Some Sunny Day is a perfect way to corrupt your Minecraft world and scare yourself to death. If you don't believe that this addon can destroy your game world, try it yourself — but you have been warned.

Credits: Pastahimself

It's A Pure Madness

I approached this addon blindly and foolishly, unaware of what awaited me. At first, the graphics began to look strange, reminiscent of a very early version of Minecraft. Soon after, I began hearing unsettling, creepy sounds. After an hour, the entities started to spawn: faceless, humanoid versions of Steve. Another thirty minutes passed, and the entities became increasingly abstract, resembling black, stringy demons. One such encounter finally caused my world to crash, effectively corrupting the save file forever.

If you are a fan of surreal, "Backrooms-like" experiences, I highly recommend this addon. Otherwise, I suggest you stay far away from it.