Who is known as the arch enemy of Sherlock Holmes?

Professor Moriarty is "the Napoleon of crime," according to fictional detective Sherlock Holmes. Though he appears in only two of Sir Arthur Conan Doyle stories about Holmes - The Final Problem (1893) and the novel The Valley of Fear (1915) - Moriarty has become known as the detective's arch-enemy, a criminal genius who rules the underworld of London.