What's the hardest game you've ever played and did you complete it?

The only game I've tried and almost immediately put down again due to difficulty was Dark Souls 3, but I think I just wasn't in the right frame of mind for it at the time. I've completed Cuphead a couple of times and Hollow Knight (though not the crazy challenges on either, just vanilla stuff). Hollow Knight was probably the toughest for me.

What's the hardest game you've ever played?