In the book, And Then There Were None, by Agatha Christie the protagonist is Judge Wargrave. In his years as a judge he was called the hanging judge because he persuaded juries to sentence people to death. It's this ability that gains him power in the group of people on the island. It's not only his past that allows him to lead the group but he has the ability to inspire confidence in many people. As we learn later in the novel he is the killer and his abilities to inspire people and lead help him commit the crimes. In the novel he acts as the detective and tries to find the killer but of course he isn't going to turn himself in. Wargrave is also a sadist. we know this because of the pleasure he takes in killing other people. He never expresses pity for the victims and it's this cold nature that lets him pull of the perfect killing spree.