i don't watch a lot of scary movies, but for me, probably something that incorporates a lot of uncertainty and also elements i can see in my own life. pacing and tenseness can also make something scary for me. i don't really find cult/supernatural things scary sometimes when everything is outlined and it's something i don't really personally believe in so once it's over it's not so scary for me.. i think when a scary movie has TOO much humour/suspension of disbelief it makes it easy to make light out of everythign and becomes way less scary too.

Honestly, the soundtrack is the scariest part of a film; it can make or break the movie for me. Yeah, it would be funny to play a song like 'Staying Alive' by the Bee Gees during a chase, but it would ruin the mood.

I think good scary movies examples can be like the Conjuring movies (or the whole series of it) and Incantation because it usually builds up fear before the scare, sometimes there might not even be the scare it's just the suspense. The atmosphere and music/sounds are great bonuses. I think what ruins some movies for me is if the story doesn't make sense at all. And I'm all for plot twists and all that; but if nothing adds up for the story it just bugs me :')

i got kind of a broad answer but like for me the thing that make horror movies is the atmospher or like the mood idk. like for example creep is a really good horror movie not because it has a lot fore or scary monsters but because the tone it presents is just awkard and off putting another example is the thing yea sure the monster is super freaky but what really sets i over the top is the feeling of paranioa it instills. for the second part i would have to agree with Rikkun cause if there is like plot detail thats total out off place it immediately breaks my immersion, i that "plot has to happen" but sometimes its to big to ignore

I think for a movie to truly be scary, it has to focus on building the element of dread
That's the only thing that came to mind atm since I don't watch that many horror movies ^^;

the scariest part to me is the anticipation and the impending doom, also when you can feel how the horrors will impact the person who lived. Just showing that surviving after a horror event (watching ppl die or be tortured) is just ar truly terrifying

For me, it's tension and suspense just eerie or grotesque characters that really terrify me!

Personally, I really like cosmic horror. For example, The Thing (1982) and the horror still holds up today. You feel a twisted kind of fear when the threat is objectively beyond human comprehension. I think what ruins a scary movie for me would be anything that lacks a lot of originality or a cookie-cutter plot. It's just not as scary when you're familiar with the pattern of the story.