Jonah 3-4

So Jonah finally goes to Nineveh and tells the people that in forty days Nineveh is going to be overturned, and you've got to think Jonah enjoyed this cause he didn't like Nineveh and it's people. It's kind of like telling your sibling, ooooh your in trouble. Nineveh had a very humble response to this message. Even the king fasted, put on sackcloth, and sat in the dust. This was a customary sign of humility.
God responded to their act with compassion and did not bring destruction to Nineveh. So good job prophet case closed right. Wrong, Jonah got ticked off because God had mercy on the Ninevites. He even prayed that this is why he didn't want the assignment in the first place and was so angry he wanted to die. God showed him and told him, what difference does it make to you if I show compassion.
A little humility goes a long way. This has been something the religious have struggled with throughout history.