Under Pressure Trophy in Aliens vs. Predator
Solve the riddle of the Ruins
How to unlock Under Pressure
This is story related and cannot be missed.
This is obtained a short while after beginning the last level. You need to find a way into a lock building, to do these you need to activate 3 pressure switches within the area. Follow these steps to find all 3 easily:
Pressure Switch 1: This one is hidden and needs to be activated first to allow you to use the other two. Climb to the top of the pyramid like structure right in the middle of the map, but be careful because here will be an android that will shoot on sight. Once you have dealt with him look around on the floor to find a vent, enter this vent and climb down to the very bottom. As you land in the water you should land right on the switch.
Pressure Switch 2 & 3: If you follow on from the first switch then these two are very close by, one is out the exit to the left hand side and one is out the exit to the right hand side. It doesn't matter which of the two switches you press first.
When all 3 switches are activated the trophy will pop.