Gungrave Gore Final Stage and Ending on Hard Difficulty 

that narrow hallway with the 250 arm cannon guys is impossible on normal or higher if you arrive without at least 3-4 demolition shots at the ready, infuriating shit. really no idea what they were thinking with the last couple of stages, every room is just "throw 250 orgmen at the player in a tiny room". rest of the game is pretty enjoyable on normal though.