There are things that people do which makes them feel an extreme sense of guilt, often ending in suicide or the least self mutilation as a mechanism to ''punish oneself'', there are also people who are relieved of the sense of guilt after receiving a punishment they deem reasonable, there are people who feel guilty endlessly even after they are forgiven. This can be observed in extreme cases when killers and rapists end up taking their own lives or most commonly when teens mutilate themselves as a form of punishment for being failures. People feel guilt for different things, one might joy at the idea to skin and mince a rabbit while an other might puke just thinking about it, one might get aroused at the idea of rape while another will feel mental stress just imagining it. There is also a contrast between intent and feeling, there are people who wanted to kill, people who brought themselves to put a knife to the throat of another person but where paralyzed, froze, and didn't manage to kill. There was a will to kill, but their body simply said ''no''. Being us social animals, these emotions and self constraints are really useful in an evolutionary sense. People devoid of any emotion are people free to cause as much chaos as possible and societies can not evolve with too many chaotic individuals. Similar emotions can be observed into other social animals or animals which were bred to be more social like foxes, ferrets, cats and cattle.
My question then would be, for an evil overlord who wants to doom the entire human population to chaos, would it be possible to release a virus which rewrites the human brain to never have any constraints? never any regret, guilt, fear ... all the other emotions should remain except those who block or punish people from or for doing things they believe to be wrong.