Scariest single player levels?

[Darth Wang]

Not the toughest, but the overall most frightening. Some of my picks:

From canon/official levels

D1 level 7 - Most of it isn't scary, but the boss room...
D1 level 14 - Huge, enemies around every corner, and that freaking music...
D1 level 17 - Enemies can attack you from all directions, lifters are freaking scary
D1 secret level 3 - Huge, dark, many enemies, overall freaky
D2 level 3 - Large, dark, a step up in threat level from the previous ones
D2 level 16 - Huge, dark, and that boss...
D2 secret level 3 - Respawning theif, 'nuff said
D2 level 24 - The boss and cutscenes make this one

Fanmade levels

Konflict at Karon level 3 - Uses the D1 level 14 music, has a very creepy and haunted vibe
LOTW Lupis mines - overall very creepy
LOTW Mine of Ganymede 1 and 2 - It's hard to describe, you have to play them
Chasm secret level - You're up against the level 24 boss right off the bat, and he's terrifying

But by far the scariest level I have ever played was one I made myself many years ago using DMB2. It was very simplistic, just a few corridors that widened into rooms with some doors, a few energy centers and robots, but for some reason whenever I played it I got this feeling of utmost dread, I would keep seeing things out of the corner of my eye and hearing things I shouldn't, like doors opening when I was nowhere near them (and there was nothing else that could open them), or hearing the sounds of robots like the thief that weren't in the level. I was so freaked out that I stopped working on it and never played it again, after having nightmares about it. (And before you ask, no, I don't still have it).

[Xfing]

In terms of scariness and the wow factor I'd say definitely D1 level 6, 7, 10, 12 and S1. Some levels are probably harder, but these are eerie due to many different factors. S1 has that entirely dark room for example.

Also, D1 level 22 obviously, if only for the music. That's probably the most unsettling tune in D1, and also the last one before the songs start over from the beginning, so it was probably originally intended for the game's finale or something. Not to mention the level is tough as nails and contains ridiculous amounts of two of the most hated mechs, the Super Hulk and the Class 1 Driller.

[vision]

I only care about D1 these days, and I'll agree that S1, S3 and L22 still shake me up a bit.

[Naphtha]

D1 Level 20 still has a bit of scariness to it on Insane for me. It's the music and the way you have to approach the later parts of the level slowly to clear them out... Not being aware of your surroundings at all times while searching for those key-holding bots could easily lead to a Class 2 Platform sneaking around the corner behind you. One of the more nerve-wracking parts of the game if you're not careful, IMO.

[Descer]

Levels themselves doesn't scare me, but if I know that there's a hard boss waitin', I'm like that if somebody touches me, I'd yell my lungs out. (Applies only to home made levels, like Driller Queen Returns.)

[LightWolf]

But by far the scariest level I have ever played was one I made myself many years ago using DMB2. It was very simplistic, just a few corridors that widened into rooms with some doors, a few energy centers and robots, but for some reason whenever I played it I got this feeling of utmost dread, I would keep seeing things out of the corner of my eye and hearing things I shouldn't, like doors opening when I was nowhere near them (and there was nothing else that could open them), or hearing the sounds of robots like the thief that weren't in the level. I was so freaked out that I stopped working on it and never played it again, after having nightmares about it. (And before you ask, no, I don't still have it).

Kind of reminds me of playing through level 7 of a WIP mission - I'm scared of going through a certain corridor because D2X-XL glitched one time and started going through every single sound in the game before doing a really creepy buzz-like noise. (I'm pretty sure it started before then, but I first noticed it in the corridor)