From Little Nightmares 2 I have found a piece that instils a mix of dread, panic and despair.
I also found a piece which has an air of Destruction and madness, but also a strange sense of hope.
From SOMA I've got two pieces which are just downright depressing
I'd put more from SOMA here but I'd have to put the whole OST in here.
From Undertale I chose Memory, basically His Theme but sadder.
From Ori and the Will of the Wisps I chose my absolute favourite song from this amazing soundtrack, representing death and sadness excellently.