noun
cunning person; crook; sly fellow
Refers to a person who is crafty, scheming, or dishonest; somewhat literary or old-fashioned, not everyday colloquial speech.
彼は見かけによらず姦物だ。
He is a cunning fellow, contrary to his appearance.
あの奸物には気をつけろ。
Watch out for that crook.
Compound of 姦 (kan, 'wickedness, craftiness') and 物 (butsu, 'person, thing'). The exact historical derivation is uncertain, but the word has been used in literary contexts to describe a cunning or dishonest individual.