The world exists within you. If you think everyone is evil, you will see evil in the world. If you think everyone is essentially good, you will see the good. Evil exists in the good. Good exists in the evil.

People do evil things in the hope of good outcomes. People do good things for evil ends.

Of course some people are just evil by nature and others are good, these are so rare that we could probably name them. The rest of us exist in a world of everyday acts of kindness and betrayals.