About 2% of the population have a neurological impairment that renders them incapable of “mirroring” the internal states of others. In other words, they have no empathy and a truncated range of emotions (which are basically power-oriented and reflect various states of the frustration of the will, anger, resentment, hostilty, etc.), so they have no natural moral compass. They know the difference between right and wrong, but it is a purely intellectual understanding that has no emotional meaning for them, so they can’t and don’t really “care” about things other people fret over as right and wrong. Consequently, they have no conscience and will put their needs and wants ahead of the rights of others. We call such people sociopaths or psychopaths.
They are simply tone deaf to the human condition but are not necessarily evil or dangerous. A acquaintance of mine who was an FBI profiler says you would be surprised at how many televangelists are psychopaths. If they are brutalized and humiliated in such a way that they become ostracized from society, they can become demoralized; which is to say, they no longer subscribe to conventional mores. Instead they become opportunistic, and they pursue their own agenda often at the expense of everyone who gets in their way. The more impulsive members of this group tend to get caught fairly quickly, labeled, and sent to prison; where they tend to get further brutalized and more or less cement their predatory disregard for others, whom they victimize.
Lonnie Athens in his book, “The Creation of Dangerous Violent Criminals” describes a sequential process of brutalization, subjugation, horrification, violent coaching, belligerency, violent performances, and virulency, which produces a person who is quick to extreme violence at the slightest hint of disrespect. It looks to me that this process could literally beat the conscience out of anyone, but probably goes very quickly with someone who has psychopathic tendencies. People who go to prison and who are subject to violence there, tend to get moved along the sequence. Once the sequence is complete, it is very, very difficult to undo.
Some psychopaths, like the fictional HBO character Dexter (who carries the trauma of seeing his mother murdered with a chain saw at age 2), find ways of dealing with their dark impulses without getting caught by following a formula or code. Lt. Col. Dave Grossman, in his book “On Killing” says that about 2% of the people in the military are full-on natural born psychopaths, and they are the only ones who have absolutely no qualms about killing. (The other 98% have a great moral resistance to killing and tend to fire their weapons in the air instead of the enemy, even when under heavy attack. If they are forced to kill anyway, as many were in Vietnam, they tend to quickly fall victim to PTSD.) The killers tend to find their way into Special Forces and commando units. Others become prison guards or Southern sheriffs, where they can indulge in cruelty and violence with impunity.
So, yes, there are definite in-born propensities to be have in ways that violate our mores and taboos and so be considered “evil” or “bad.” But there are also processes that can probably bring these out in anyone.