"You're despicable!" speaker voiced by Mel Blanc

DAFFYDUCK

This looney black-feathered troublemaker often squabbles with a certain rabbit over hunting season.

This clue points to Daffy Duck, the fast-talking, egotistical cartoon character famous for his outbursts. Mel Blanc, the legendary voice actor, brought Daffy to life and often delivered his signature line, "You're despicable!" in a raspy, exaggerated tone. The answer combines "Daffy" and "Duck" into one word, which is how the character's name is typically written in crosswords.