Dishonored offers action, adventure and stealth in one game. Although you can go all out on your enemies in the game, I am pretty sure stealth fans will prefer the Stealth route and avoid killing any hostile target to unlock Ghost and Clean Hands achievement.
You are rewarded with clean hands achievement if you complete the game without killing anyone while ghost is your reward for avoiding detection and avoid killing anyone but the key targets throughout the game.
You see what the developers did with these two achievements? If you are a casual player, it will take you at least two playthroughs to unlock these two achievements. Unless, you have the patience to reload your every fail and save rigorously, and of course, you still have to follow our general Clean Hands / Ghost Tips.
If you are looking for a more in-depth walkthrough, you can read our detailed guide on each mission by browsing through the links below: