For this particular achievement all you need to do is complete the game on easy or higher (any difficulty)
The game is not very hard but i recommend playing it in two player as it much more fun. Try to play it on contractor first whch is not very hard unless you are playing it in singleplayer. (The AI is very poor)
Collect all collectables and pick one of the morality choices, either good or bad, so you get the achievement for just choosing one throughout the game.