Certain serial killers maybe? I get that people are fascinated by them, but to me such people are oddly boring. Their crimes are horrific, but the justifications (if not outright delusional) seem to be just "I can do whatever I want if I find a way to get away with it".

Most other people we might consider 'evil' have more moralistic justifications - such as religious fanaticism, or nationalism, or revenge against some perceived enemy. Not that this makes them right in absolute terms, but presumably they do not consider themselves evil.