It says "all possible scares", but you actually only need 5 specific ones. (There are at least three scares not included.)
1: On the second loop, see the falling suit, then open the vent for a scare.
2: On the third loop, interact with one of the cryo chambers.
3: On the third loop, look out the large window for a couple of seconds.
4: On the fourth loop, go up to the monster in the recreation area/living quarters.
5: On the fourth loop, do not take a picture of the petri dish moon, but continue through the door. When the looping lab comes, again ignore the petri dish and go through the door. The monster will pop down for a final scare as you move towards the next room.
This should unlock the achievement.
(There is also a scare where the monster pops out from the ceiling just before the lab/loop door, and there's an unnerving situation where all the hanging suits seem to be looking directly at you. Finally, there's one at the end of the burning loop.)