In the end, what happens to the king and the duke? How does Huck their fate? What does this show us about huck?

Both men are tarred and feathered by the townspeople! This shows that Huck did not live by their code. Although Huck would sometimes lie or even steal, he had definite boundaries of right and wrong. Huck did not share any of the King and Duke's nastiness. Huck doesn't mind giving these two clowns up.