He was known throughout the town as a crook.
Don't be fooled by that swindler.
詐欺師 is the standard modern word for a swindler or con artist, whereas 不徳漢 is a rarer, more literary synonym.
Compound of 不徳 (immorality, lack of virtue) and 漢 (man, fellow). The exact historical derivation is uncertain, but the term likely emerged as a literary coinage to describe a man of low moral character.