Depends on what ending you want to get and the difficulty.
— Ending A (Coffin Ending): Mrs. McDonnell goes insane and buries herself alive in a coffin.
— Ending B (Reality-Bending Vent): Mrs. McDonnell becomes trapped in a vent and is killed by a small, humanoid creature made of light.
— Ending C (Good Ending - Burning the Nun): Mrs. McDonnell slays the Nun by burning her alive using the lighter and fuel found in the game, and is forgiven.
— Ending D (Acid Pit Ending): Mrs. McDonnell gets trapped in a room and is killed by the Nun with acidic vomit.
— Non-Standard Ending (Barbed Wire): Mrs. McDonnell becomes trapped in a barbed wire pit and is killed by the Nun.