The differences between this difficulty and the regular difficulty are that every enemy that you encounter will be able to kill you and whenever you die you will have to start back at the beginning of the mission.
I suggest that you do NOT rush this for when you try and go quickly you make mistakes. Move slow when you can and be sure to use the to see further around the screen. For example you should use the to look around for turrets. With time and perseverance you should unlock this achievement in no time.