Some are so efficient at spreading fear and dissent that they've become the most powerful people in their respective worlds. The personal philosophies of these characters drive them to make others afraid of them.
Death Note's Light Yagami spread fear and chaos through the killings he conducted under the "Kira" alias. He became so prolific that even the Japanese Task Force hesitated to accuse him of anything. After all, L was not able to survive regardless of his great intellect, and they were much less competent than he was.
Over time, entire movements grew in support of Light and his cleansing of "societal corruption." What they failed to understand was that Light had developed such a god complex that he was perfectly comfortable becoming a murderer himself if it meant preserving his secret identity.