Instructions
Die 51 times in the single-player game on any difficulty and then complete it. Save the completed game when you are prompted.
Load a new game from your completed-game save file and play until you obtain your equipment from Metal Gear Mk. II.
Pause the game and go to the Camouflage menu. Select the "Octocamo" option and then go to the manual camouflage menu.
Scroll through the camouflage patterns to "Corpse Camo" and select it. Exit the menu and resume the game. The Corpse Camo will be equipped.