Try to add some suspense. Maybe don't make this the opening scene, write between ten and thirty minutes of introduction to the characters, maybe give both of them a lot of humanity, then, when the death comes, BAM! It hits the audience, who are all like WTF?! This could all be done with thirty minutes at most, leaving plenty of time add an assload of story. Also, try to make the beginning--even the credits--as nice and family-value-filled as possible, then start adding a tad bit of darkness to the story as the cheating comes into play, then make the death scene as inhumanly violent as posible without actualy showing much other then, of course, the blood in the ceiling. Another idea, don't give it any main titles.