Good Behavior Trophy in Silent Hill: Downpour
Completed the game on any difficulty without killing any monsters.
How to unlock Good Behavior
Just as it says, you must complete the game without KILLING any monsters. You can incapacitate them, but make sure that they don't die during combat (make sure they don't disintegrate after they fall to the ground, if so, reload an old save to restart). This is actually easier than it sounds as you can just run by everything and avoid fighting completely (although "The Bank" sidequest that does require killing, so avoid doing it during this run). If you are ever worried that you might have killed something by accident or not, always check your statistics screen under the pause menu (it's almost at the bottom) to make sure it's still 0. "Bosses" do NOT count towards kills. After you complete the game with no monster deaths, the trophy will pop!
Note: Near the very end of the game you will ride an elevator and it will make stops at different floors where you have to defeat some enemies in order for it to resume. Make sure you just incapacitate them and not kill them (although I'm not 100% positive you even can). After they are all down, the elevator will resume and they will disintegrate, but as long as they were just incapacitated, they will not count against your total.