Not quite, my theory is that the ability to commit atrocities is (much like I would assume your evidence would suggest) certainly evident in every being on the planet.

Mass atrocities and murder on large scales is simply a result of many people getting together, regardless of how they do so. Because it's the individual, and not the organization that is the actor, your point that "governments have murdered more people than corporations" is bunk. Given more power, any organization is capable of such crimes. For example, the Catholic Church.