Complete the Campaign on any difficulty without dying.

For this achievement, be as careful as you can, take cover where ever you can, and be sure you dont stand near anything that can explode so the Special Forces wont blow them up and kill you. The only real danger is Alma and her Ghosts. Make sure you have a good supply of health in the final levels, and you should be able to survive their attacks. Just dont let Alma touch you. A single touch will take you down.