[it's hard to give suggestions when he doesn't know the nature of the objective, but. . .]

If it involves killing someone, then again, you could assist them in finding a voluntary victim. You could also frame someone, or find someone willing to take the fall on their behalf.

There's no pleasant way to go about it. I imagine, based on our low Villain numbers, that the populace would be far more willing to spare them despite their crime, anyway.