Dead Boys (Coalition soldiers) in Rifts. The typical grunt soldier is a perfectly normal person when he's not slaughtering villages of helpless aliens or shooting mages in cold blood. The sad truth is that they've been indoctrinated from birth to believe that all aliens and magic constitute a very real threat to them and their loved ones. It never occurs to most Dead Boys that they're killing people just like them, with hopes, dreams, and their own families. Most of them can't even read (the Coalition States have a strong anti-literacy stance), and thus have no way to learn anything but what the Coalition teaches them. They are generally used as stock villains in Rifts games set in or near Coalition territory, and they do commit rather horrific acts.
It's explained by fluff that many of the "bad guys" in Warhammer 40K are actually just this trope; common soldiers obeying their commanders, many times not even aware that said commanders are in open rebellion if not outright Chaos cultists. It's even worse in some of the larger ships in the Imperial Navy, whose populations can match those of small countries; entire generations live and die on them, some not even leaving assigned areas, and are so conditioned to obey orders that they neither know nor care whether they're subduing a group of heretics or virus-bombing a pacifistic pre-industrial society.