Gaddafi and Sadam are excellent examples of darkworkers. If you think of it within the darkworking/lightworking paradigm, they are simply people who are good at consuming energy. They direct energy into themselves.
Read this for more insight: Are Darkworkers Evil?
With regards to what the second poster said, I disagree that a person who sacrifices himself for others should be labelled "good." Most people juxtapose between giving and receiving energy. For every job that you manage to get, a number of other applicants would have to fail. All competitions have many losers, with only several winners. In such situations, are you not "sacrificing others for yourself?" Are you a bad person then?
I think what the OP is trying to ask is "Is good and evil inherent in people?" This is a philosophical question, with no easy answer. Try reading philosophical texts on good and evil.
Some of the answers as to what is evil and what is not here seems to point towards moral relativism, i.e. "whether something is evil or not depends on who you are in relation to that subject." I'd like to point out that morality cannot be subjective, because then it wouldn't be able to supply an objective answer to the question "how should we live?" In other words, it would be perfectly fine if we choose to be immoral, if morality is subjective.