In this chapter you can find tips that can help you to unlock the secret achievement in Outlast II.
The only chance to get this achievement is in Raining Blood section in Lamentations chapter. At a certain point you found yourself in a hallway covered in blood pouring down from sprinklers. At that moment nothing wants to harm you there and the demon is not following you. Wait a moment until the floor is completely covered in blood, take a run-up by using sprint and slide after a few seconds.
You probably won't get it in your first try but your time is unlimited so you can do this over and over again until the achievement/trophy is added to your account.
If you are past this chapter then remember that after completing the game you can use a new saving slot to go back to this section and complete it again, this time focusing on this achievement.