Ended ALERT status while wearing the Corpse Camo.

To unlock the Corpse Camo, you must use the Continue option over 50 times and finish the game - you will do this during your Puma/Chicken playthrough.

This is a quick and easy trophy to get, however getting the Camo may be a small bit of a grind. Equip the Corpse Camo at any part of the game once you have it and simply make yourself obvious to an enemy. ALERT status should initiate and the trophy will unlock when the ALERT status ends.