_______ is a literary device in which ultimately virtue is rewarded and viciousness is punished.

Poetic justice, in literature, an outcome in which vice is punished and virtue rewarded, usually in a manner peculiarly or ironically appropriate.
The term was coined by the English literary critic Thomas Rymer in the 17th century when it was believed that a work of literature should uphold moral principles and instruct the reader in correct moral behaviour.

Source: Britannica.com