Last one for now. Point is, I guess any song can be dark as hell depending on what you picture happening with it. Like here: "don't believe me, just watch" is pretty messed up depending on what you're doing.
Front Line Assembly has lots of songs that sound like the world is ending horribly. With artwork to match.
When trying to get into that mind set I find instrumental heavy metal or instrumental hard rock does it for me.
I Got the full OST for Nier: Automata just for that. And it was worth it. It's.......just PERFECT for that setting.
I adore this channel. I myself listen to their work while writing. Every other comment on that first video references games like Fallout, the Metro series, the STALKER series, The Last of Us... In other words: they got it right.
I've always enjoyed Lorde's darker and more depressing cover of Tears for Fears' Everybody Wants to Rule the World for planning my world's conflicts: