Oooh, Horror Movie Recs call, and Peebs shall answer. Some of these are a bit tangential on the creature part, but there is always at least one (1) Creature.
The Void (2016) Mostly lovecraftian horror, following a supernatural siege on a mostly-shuttered hospital, but there's some incredible and deeply disturbing practical FX work in the back half of this movie. To quote my brother about one particularly disturbing sequence "that was literally hell."
Glorious (2022) Man finds himself trapped in a public bathroom with an elder god in the neighboring cubicle and would you look at that there's a (glory)hole and everything. A bit wonky on the pacing but fun none the less.
Attack The Block (2010) A bit more on the sci-fi horror-flavored adventure side of things, but the creature work in this film is excellent, both in design and its use. Also worth a look for a pre-Star Wars John Boyega and Nick Frost, as always, being a delight.
Creep (2004) note: not the Mark Duplass one, which is a creature feature only in that Duplass is a bit of an Creature. Woman trapped in subway with some sort creepy crawly. Not an outstanding beaste, but there's at least a bit there there.
The Tunnel (2011): Aussie TV team goes into tunnels that they're not supposed to know are there, finds out why they weren't supposed to do that. We don't see much of what's there, but it does a good job of making a lot with a little, Blair Witch style.
Final Prayer (2013): UK investigation horror. Something's funky's going on in a church, but is it a scam, a miracle, or something way way worse? Very loose on the "creature" here but honestly I just gotta have more people see this movie. Perhaps one of the most harrowing endings in any horror movie I've seen?
Noroi: The Curse (2005) Japanese faux documentary about some supernatural business going all black hat. A bit slow on the pacing, but the build-up is absolutely incredible. Come for the "maybe there's something here," stay for the evil fetus mega-spirit.
Gonjam: Haunted Asylum (2018): Streaming-style Found Footage. People with more A/V equipment than sense go to allegedly haunted asylum looking for a scoop. They find way more and way worse than they expected. A couple of these scares should by rights be decade-defining
One Cut Of The Dead (2017) Ok, this movie is just silly, but it has a tremendous heart to it. I will only say the following to not spoil the delightful surprise: the first segment of the movie is... very strange seemingly on purpose, stick with it.
Society (1989): An absolute body horror classic, but I'm including it on the off chance that you haven't experienced the sweet infernal madness that is The Shunt. A teenager comes to discover that his family and community is involved in some Cult Conspiracy shit, and that they have designs on him that are quite contrary to his well being.
The Stuff (1985): A classic piece of horror satire to bring us home. The new Superfood turns out to be capable of a bit more than advertised, and may have designs on the human race. Some really fun goo-based violence in this one.