What are the hardest JRPGs you know of?

I've been playing RPGs for years and I'm interested in hearing about difficult games to challenge myself with. What are the hardest and most brutal RPGs that you know of? I want to hear about games that will show no mercy and will kick my ass eight ways to Sunday - ones that are even harder than the PS2 version of SMT: Nocturne on Hard mode.

(I will have to specify, though, that action-RPGs don't count. FromSoftware games are known for their difficulty, but it's usually the action elements and not the RPG elements that make Souls-like games hard.)

So, what's out there?