Scary as in one actually causing you (to whatever degree) something nearing being fear.
Sanitarium (1998 point and click adventure) had a number of rather strange and bleak situations.
I mostly played less dark adventures, like Broken Sword or the first Gabriel Knight (which was, still, less dark than Sanitarium).
Others here, in some past thread, had mentioned Harvester (which again i never played but looked quite gruesome from the pics and plot i looked at).
The old Microprose game Shadow of the Comet, which was based on Lovecraft lore, also was somewhat ominous.
Sanitarium (1998 point and click adventure) had a number of rather strange and bleak situations.

I mostly played less dark adventures, like Broken Sword or the first Gabriel Knight (which was, still, less dark than Sanitarium).
Others here, in some past thread, had mentioned Harvester (which again i never played but looked quite gruesome from the pics and plot i looked at).
The old Microprose game Shadow of the Comet, which was based on Lovecraft lore, also was somewhat ominous.