The Breach was pretty good and the good stuff you want.
Underwater isnt any official Lovecraft story, but it absolutely comes across as one. You have a few minutes of intro and then its discomfort all the way through (extra points if you dislike deep sea or tight spaces).
Dagon (2000) isnt good, but its Lovecraft through and through and never lets up from the start.
Event Horizontechnically not Lovecraft, but definitely has some elements and is a fairly nonstop science fiction horror.
I just watched Smile, and will absolutely agree it was worth it.
The Mist (2007) has all of the fear of the unknown combined with creatures that seem otherworldly. A little slower, but with some horrific scenes, and also a locked in a building with survivors situation.
Re-Animator (1985), definitely cheesy and low budget, but its incredibly screwed up.
Prometheus is a very divisive movie and part of the overall Alien universe, but it has heavy emphasis on ancient designers, biological creation, and things humans think they can play with that far exceed our understanding. Its very story heavy so starts a little slower, but its fairly dark and suspenseful until the good stuff starts. Its not the typical Alien face hugger and xenomorph.
If you like Prometheus, Covenant is the next part of that and continues the story (still pre-Alien lore wise).
Annihilation is also story heavy, but it delves into the unexplainable, otherworldly creationism, and once it starts it is quite unsettling.
The Endless is good if you want something more story related that is both fascinating and terrifying. Basic premise is cult survivors revisit their old cult because of an odd video, and realize the being the cult worships may actually exist. I enjoyed it as a low budget and surprisingly well executed story, but it does lack the gore and body horror; most of the fear comes from the slow understanding of their surroundings.
The Lighthousethis one issomething else. No direct Lovecraft link and a very visually creative slow creep. But its dark and mysterious from the start, and slowly ramps up the insanity all the way through. Its a fantastic movie, but its so odd in some ways it wasnt as enjoyable to me personally.
For stuff that I just enjoyed and is fairly screwed up, Splinter was pretty unique and very disturbing.
Ravage (2019) is also very screwed up, and pits a capable survivalist against cruel people in the country. Not a slasher, more a revenge flick, but the ending (to me) made it seem like the story isnt over, and its left up to our imagination what happens next.
Last Shift (2014). Extremely disturbing movie and right up there with Smile on ones I recommend that have nothing to do with Lovecraft.