can someone recommend me some underrated horror movie

Lake Mungo the purge, anarchy

Trick 'r Treat (2007) slips under radars lately because it's from the mid-00's, which isn't old enough to be a classic but not new enough to be a big thing.

Climax (2016) is an arthouse horror film about a group of dancers who take acid. It's filled with artistic shots, crazy camera angles, long no-cut scenes, and more. It's also in French. It's directed by Gaspar Noe, and like all of his films, it's really not super accessible, but it's probably the single-most disturbing film I've ever seen. Some of the splatter films/torture porns are probably up there, too, but this one is intense.

Husk - Join the Harvest and The Grudge

The Invitation' (2015), Session 9' (2001), The Blackcoat's Daughter' (2015), The Faculty' (2018) ,The Wailing' (2016), Ju-On: The Grudge' (2004)

Watch Noroi: The Curse, it's a japanese found-footage style movie. Not very popular but it's pretty well done and isn't full of cliches like most horror movies

I haven't seen Hereditary mentioned yet. That's a good one.

Bonus: This is more of a revenge thriller, but I'd recommend I Saw The Devil (korean movie).

idk if its underrated but a quiet's place is very good also try watching some ARGs if you like short horror content

a quiet's place is really good and u should defiently watch it

Definitely recommend It Follows

Though its pretty weird at first i think Krampus is pretty under rated.