Paul Morphy
Morphy taught himself, and by nine he was good by the standards of the local players. At 12 he defeated the Hungarian professional Löwenthal in three casual games. Then he played little chess until he had qualified in law in April 1857. He then entered the first American Chess Congress in New York, and won it easily. Next, he accepted an invitation to play in a tournament in Birmingham, England. That started his famous European tour. He beat everyone of note in England, except Staunton, who avoided a match. Staunton was earning money editing Shakespeare, so his absence from chess was not just an evasion.