Blackguard is a dated word which can be used as a noun or a verb.
Verb: To blackguard means to abuse or disparage; to be rude and foul (to someone). For example, when Alison asked Rocky to pay his debt, he blackguarded her until she left the room.
Noun: A blackguard is a rude or unscrupulous person; a person who behaves in a dishonorable or contemptible way. For example, Rocky has been a blackguard since he was a child, but Alison still thinks he’s polite sometimes.