Nightmare of Druaga - FD (PS2) has it's moments of "Oh shit here we go". It can get *extremely* difficult depending on many factors.
Wizardry IV (appleII, PSX) is the hardest arbitrary CRPG ever. If you don't know what I mean by arbitrary then you've never played it.
Nethack (and similar roguelikes) are all arbitrarily impossible as well.
If you think those are hard NES platformers you should check out Blaster Master.