You are the second person to bring up sociopaths as if they don't match the definition of evil I wrote above. The thing is, they are the very personification of lacking empathy. They believe that their own welfare is more important than anyone else's. They don't see that as evil, they see it as the way of the world.
The point is they don't rationalize or justify what they do, they simply don't care. They know it's wrong (by societies/normal people's) standards, but it doesn't violate their own.
This is what I consider evil, and I think it's important to separate it from people who think what they are doing is ok. I.e. "Someone else would have done it anyways", a thief who steals from a bank because "they have insurance" or "they are rich assholes who don't deserve it", or a dictator who tries to do what he thinks is best for the country even though his policies are bad.
