Instructions
Play through "Metal Gear Solid 4" until you reach Mantis. She appears after you exit the Command Center in Outer Haven.
Avoid Mantis' attacks. She only has one move: She disappears and suddenly reappears beside you, immediately attacking you. You can avoid the move by not standing still when she disappears.
Aim your weapon at the red doll Mantis holds. Press "R1" to shoot the doll, making her drop it. Pick up the doll to permanently add it to your collection.
Equip the red doll instead of your normal weapon. Press "R1" to fire the doll at Mantis. You only need one shot to force her out of her suit.
Equip your tranquilizer pistol instead of the red doll. Fire at the unsuited Mantis until her health bar is fully depleted. Your tranquilizer rounds will not kill her.