When it comes to movie ratings, the NC-17 or X certification was as strict as it could get, meaning that these horror movies were truly for adult eyes only. While the already harsh R rating meant those under 17 years old required an accompanying parent or adult guardian to see the film, these classifications blocked all young people from seeing these controversial, divisive, and highly violent movies. Many of these horror films pushed far past normal boundaries of acceptability and were likely to give viewers nightmares no matter how old they were.