But it displeased Jonah exceedingly, and he was very angry.  And he prayed unto the LORD, and said, ‘I pray thee, O LORD, was not this my saying, when I was yet in my country? Therefore I fled before unto Tarshish: for I knew that Thou art a gracious God, and merciful, slow to anger, and of great kindness, and repentest thee of the evil.  Therefore now, O LORD, take, I beseech Thee, my life from me; for it is better for me to die than to live.”  Jonah 4:1-3 (KJV)

This prophet who despised the people to whom the LORD had sent him, did not want to see this people forgiven, but rather his desire was to see this mass of people destroyed.  The LORD was having mercy on Nineveh, when He saw their repentance.  Due to their sin Nineveh was destroyed about 100 years later.

Of all things…