Adventures of Huckleberry Finn
The Duke and The King
At first these two seem like some great comic relief. But then we realize they're complete, shall we say, jerks, for lack of a stronger and more inappropriate word. The king in particular is immoral, disrespectful, self-serving, and manipulative. They also put a barrier or two in the way of the protagonist's journey by selling Jim back into slavery—which is a pretty antagonistic thing to do.