User blog comment:Ngh93/What REALLY makes a villain a Complete Monster?/@comment-27818776-20150326235216/@comment-27818776-20150327202339

The complete monster is a special kind of heinous, though. A villain is expected to commit evil actions, but a CM stands out due to going beyond the standards that the other villains are confined to.

For example, as I have mentioned, an evil overlord isn't automatically a CM unless they commit atrocities like mass genocides to make them stand out more. Serial killers aren't automatically a CMs either, unless they are particularly brutal in their trade. It usually depends on how the story presents a hero/anti-hero. Say that an anti-hero kills assholish characters whereas the villain in question kills five innocent bystanders. That doesn't affect the heinous standard. If the anti-hero also killed innocent bystanders during their journey, then we would have a problem there. So, really, it depends on how the work establishes the characters that the hero kills.