Werewolf of London

Jack the Ripper; obviously it was Sherlock Holmes. Consider the evidence. Holmes had the medical expertise that is often attributed to Jack the Ripper (Holmes and Watson first meet at a hospital laboratory where Holmes has been beating corpses with a stick to study how they bruise). He is emotionally detached to the point of callousness. Holmes is prone to depression which he attempts to relieve by injecting himself with cocaine. He is never known to have formed a sexual relationship with anyone. He was accustomed to prowl about the East End in disguise, trawling the lowlife there. He would have had a close professional acquaintance with the investigating officers and the inside knowledge that would bring - allowing him to stay one step ahead of his pursuers. He possessed the arrogance that would have risen to the challenge of committing the perfect murder (several times). It all fits.