I personally believe that God will be the one who ultimately serves true justice to everyone. I also believe that torturing people is wrong, no matter who is doing it. I'm in favor of just giving a mass-murderer the death penalty, rather than doing something as inhumane as torture, or as costly and a waste of tax money as keeping him in prison for life.
So no, i'd say it's never right to torture. I would just kill him and be done with it.