I checked the manuel for the gamecube game on how to subdue an enemy and it said we had to stun them with the car keys, when I do this to an enemy until it works no more, my score sheet doesn't say I subdued him. Also when the game says I got a special feature like assassination for multiplayer, I still can't play it. Is something wrong with my game of something? Please help.
Crouch, and sneak up behind an enemy with a gun. They will drop their weapon and surrender. Equip your fists, and punch him in the face.
I did this three times on The Exchange:
1/ The first guard, in front of the building you start on. You're facing a sniper-guarded archway when you start. Crouch, and sneak down the stairs. The guard will be in front of the door.
(It's best if you put your silencer on your P77/P2K when you start, because if you fire and it isn't supressed, the sound will alert nearby guards.)
2/ The guard patrolling the road past the sniper-guarded archway. When he turns around to face away from the arch, sneak up behind him.
3/ The guard in front of the wine truck. When he turns his back to head down to the wine cellar, then aim at him, whilst crouching behind him.