What’s the scariest reveal in a horror movie?

Someone mentions it in the comments and it’s not a movie, but what immediately came to mind is when Violet finds her dead body in the first season of American Horror Story. Dang. I did not see that coming and I felt so very sorry for her — trapped forever in the house where she was murdered and not even realizing until that moment that she’s a ghost and has been for weeks (?).

Since she did not recall her own death, as a ghost she was continuing to be friendly with her own murderer too (who of course very much knew what she was). Argh.