On this one, I have a few examples of particularly tough games.
Persona 1 (US) was undecided. It started extremely easy and the difficulty ramped up steeply beyond the second half. Last boss was at the end of a one-two hour dungeon (since the last save point) and can pretty much one shot you. Maybe I was underlevelled.
Wizardry 4, Return of Werdna was extremely (and unfairly) difficult. Some of this was due to its old school system, but not all. Enemy rogues can steal important quest items from you, returning them to their original spawn points. Some puzzles required prior knowledge of the Wizardry series to answer. One floor is a maze that changes as you move through it, and can change in such a way to box you in and can't change it back. Combat was also consistently challenging throughout. Save and reload tricks rarely work either, as this causes all enemies to respawn. It's been dubbed the hardest rpg out there and I agree.
