You need the weapons Death Scythe and Silver Gun for this trick. In hard mode when you encounter Graham, equip your Death Scythe in the first encounter with the soul Giant Bat. Keep hitting Graham with your scythe, use the Giant Bat soul when necessary to dodge his attacks. When he moves to the center and makes his meteors revolve around the room, equip the Silver Gun and move to the far right. This way, you will not get hurt. Keep shooting him until he goes down. When he goes to his ultimate mode, equip your scythe again and keep low, striking while holding Down. Slide when necessary to avoid the laser at the top. Killing Graham this way will result in minimal damage and a fast kill.