Hereditary
The beginning of the movie was genuinely haunting with just how real it felt. Especially due to the acting, which really made the movie; I just couldn't help but imagine it as my own family instead.
Although I loved the rest of the movie as well, it was a lot less frightening when they introduced all of the supernatural elements. It still was able to freak me out beyond belief with all of the people lurking in the background and stuff, but it lost me a little bit. I feel like it would have been scarier and more impacting if it had stayed based in reality. (For example, maybe no floating headless people...)
That doesn't mean that it's not still a fantastic film, and one of the scariest horror movies that I've seen to date. I always love when something is able to be scary without cheap jumpscares or excessive gore.