Honestly I dunno.
Probably some 3rd gen game like Ninja Gaiden but I consider these games unfair not hard, because the "hardest" parts are usually because of hardware limitation and not so good controls above anything else.
Maybe Demon's Souls, then.
I'm replaying Dark Souls and it's feeling like a walk in the park, either it's easy or cheap, well, I'm much more experienced with this "genre" nowdays.
Didn't remember Dark Souls had such bad controls and framerates problems though, it may have a lot more on it but Demon's Souls is a lot more polished than it. A LOT. Dark Souls 2 as well, but that's a newer game.