Professor Moriarty

He is extremely tall and thin, his forehead domes out in a white curve, and his two eyes are deeply sunken in his head. He is clean-shaven, pale, and ascetic-looking, retaining something of the professor in his features. His shoulders are rounded from much study, and his face protrudes forward and is forever slowly oscillating from side to side in a curiously reptilian fashion.
“He is the Napoleon of crime, Watson. He is the organizer of half that is evil and of nearly all that is undetected in this great city. He is a genius, a philosopher, an abstract thinker. He has a brain of the first order. He sits motionless, like a spider in the centre of its web, but that web has a thousand radiations, and he knows well every quiver of each of them.”
“His career has been an extraordinary one. He is a man of good birth and excellent education, endowed by nature with a phenomenal mathematical faculty. At the age of twenty-one he wrote a treatise upon the binomial theorem, which has had a European vogue. On the strength of it he won the mathematical chair at one of our smaller universities, and had, to all appearances, a most brilliant career before him. But the man had hereditary tendencies of the most diabolical kind. A criminal strain ran in his blood, which, instead of being modified, was increased and rendered infinitely more dangerous by his extraordinary mental powers. Dark rumours gathered round him in the university town, and eventually he was compelled to resign his chair and to come down to London, where he set up as an army coach.” (Sherlock Holmes)