I was talking to my group about Game Mastering a few Black Crusader sessions in the futur and our veterant game master told me the golden rule about running a evil game.
You have to make sure that the player's character fear their boss. Think He-Man style. What keep his croonies in line? They feared Skeletor. Sauron in Lord of the ring is also a great exemple of controling with fear.
You could hear/encourage your players to make comments like: " I would crush you right how, but I wont do it because of our boss. If he was not there, I could kill you in an instant!"
I hope it helped.
Life is too short for games that suck.