Does anybody knows some wads that have a more horror or unsettling atmosphere ?

[Shepardus]

Not an area with which I'm very familiar, but the first thing that comes to my mind is Maskim Xul:

 

[Steveb1000]

I am currently playing ALT and it has a strange, creepy, unsettling feeling. 

 

Think it's due to the level designs (which feel like slightly off versions of Doom 2 levels) and the sound effects and alterations.

[PsychEyeball]

This is sort of a one-shot deal, but Scythe 2's MAP16 definitely can qualify as horror. 

[Fabricator]

A ton of slick recommendations in this thread, as a huge horror fan I love spooky / tense / atmospheric WADs!

Nihility: Infinite Teeth by @years is a certified hood classic and absolutely fits this criteria to a tee! :) Kinda like a demented lovechild of the DOOM Alphas and The Shores of Hell, with some dope custom enemies and unreal use of ambient sounds. Absolutely oozing with dread and isolation, a pure survival horror experience... love it! (Pairs really well with DOOM Delta too!)

Dimension of the Boomed by @Urthar while not necessarily "scary" in the traditional sense, is a solid mash-up of Quake 1 themes into a single cohesive episode, so it has that otherworldly atmosphere and hostile attitude the OG game had / has. Another one with custom monsters and ambient noise that really creates a super-immersive experience. Also has a demo for a WIP sequel and has inspired a community project in much the same vein!

 

[K_Doom]

Interesting question, taking advantage of the post I take the opportunity to ask if anyone has seen any wad like "Backrooms" and liminal spaces?

[Somniac]

I had a go at making a more horror/survival themed map recently

 

 

I also really recommend the DBP Dead But Dreaming which really nails the Doom/Doom 3 mix.

 

[CrocMagnum]

Here're a few Lovecraftian-themed wad:  

 

Rylayeh: 10 Levels with a creepy atmosphere. 

Beyond Kadath: 1 very large level with good pacing, satisfying combat and a music which sets a proper horror mood. 

Strange Aeons: 45 new levels in 5 Episodes. This is total conversion with new weapons and monsters. Great stuff. 

[Lime]

Reconstruction/Decomposition has a really unsettling atmosphere because of the unfamiliar custom textures.