This is a story related achievement.
Like every game, the harder difficulties can cause issues for some players. I suggest you play through the game at least once to learn all the movies and the general dynamics of the game. If you don't feel like running through the game more than once, start out on hard.
While playing through, make sure you pick up and solve as many of the riddles as possible to help build your XP level. The more you build on your character; the easier the game will be in the long run.
Look through the secret achievements for tips on how to deal with the bosses you may be stuck on.
These achievements do stack, so playing through on Hard will unlock the achievements for the Easy and Normal difficulties.