I wonder if rent-a-cops, armored car personnel, or blackwater (Xe Services) folks ever take offense about how many armed henchmen are brutally killed in videogames? They had it coming. Shouldn't have taken money to guard things!
I like it when you have the option to pretend to be guard and get to maintain a conversation with another guard, he has you over for dinner, you build a relationship with him or her, you're named the god father of the other guards first born, then one day: stab 'em, casually plant explosives or steal the plans or whatever you're supposed to do, and leave. Long timescale infiltration: you lose points in time, but gain points in brutally murdering someone who thinks you're their best friend.
My favorite type of killing is, when you trigger an alarm, figure out what door the armed response exits from, then headshot guard after guard as they file out one after the other.