Jonah 4:1 says this outcome "displeased Jonah exceedingly, and he was very angry." The Hebrew is emphatic: vayΔra' el-Yonah ra'ah gedolah, literally "it was evil to Jonah β a great evil." He was enraged that the mission had worked. His prayer reveals why he ran in the first place: "I knew that thou art a gracious God, and merciful, slow to anger, and of great kindness, and repentest thee of the evil." He had always known God might relent. That was the problem. He didn't want Nineveh saved. He wanted them judged. He had run not from inadequacy but from theology β he knew exactly who God was, and he didn't want that God applied to Nineveh.
God prepared a gourd to shade Jonah from the sun while he sat watching the city. Jonah was "exceeding glad of the gourd." Then God sent a worm to kill the gourd overnight, and the sun beat down, and Jonah fainted and asked to die. When God asked whether Jonah had a right to be angry about the gourd, Jonah said yes, even unto death. God's final response is the entire point of the book: "Thou hast had pity on the gourd, for the which thou hast not laboured, neither madest it grow; which came up in a night, and perished in a night: And should not I spare Nineveh, that great city, wherein are more than sixscore thousand persons that cannot discern between their right hand and their left hand?" The hundred and twenty thousand who "cannot discern between their right hand and their left" is understood to refer to children β six figures of children God uses as the final argument. Jonah doesn't answer. The book ends. We never learn if he changed.