Basic villain operating procedure should be to put safeguards into place to ensure loyalty of minions. How many stories would have turned out differently if the big bad had done this?
And we don't mean just feeding annoying ones to piranhas, although that's good for general all-round laughs.
Luke: Mother! Save me! I feel the good in you!
Anakin: Nice idea.
Anakin: Padmé! You say you love me? Save me or remember forever that you didn't!
Palpatine: You fool; she cannot save you. I built cooperation measures into her armour.
Darth Vader: He can instantly turn off my life support.
Anakin: You manipulative wretch.
Palpatine: I granted her this life; it is mine to rescind.
Luke: I'm not sure I agree with that general philosophy...