Utterly Mad

If you have ever played FEAR, that is what I consider to be excellent horror. You know why the abomination acts the way it does at the end, but up until then Alma is an unknowable, violent, and very powerful force. This is combined with how the game handles jumpscares. The only flat out in you face jumps are is actually a Human. The others, with Alma, tend to be blink and you miss it corner of the eye apparitions. Hardly lovecraft, but still effective.
also, on topic of scares, games where you KNOW its there and just not bugging you, until it randomly decides to start bugging you, tend to be more compelling scares, because you KNOW,its there, you are just helpless to stop it.