Players 9, 10, and 11 are not neutral. They can't run triggers either.
QUOTE(UCM_AXEL_)
However, everytime I place a unit that belongs to Player 9, 10, or 11 and make it the enemies of someone...
Not possible.
QUOTE(Toothfariy)
i've tried it before, they all hit their target once when i set an ai scrpit.
Not possible.
You said you got a Player9/10/11 unit to attack something? I'd love to see that.