Manasseh starts reigning over Judah at the age of twelve and continues for fifty-five years.
Unlike his father, he's a bad king. He rebuilds the high places that Hezekiah had demolished, builds altars to foreign gods in the Temple, and brings back the worship of sacred poles and of Baal.
He also sacrifices one of his sons in fire and consults with wizards and mediums.
He puts a carved image of the Asherah (a goddess considered to be a consort of God by some) in the Temple, further disobeying the laws against polytheism God gave to Moses.
Manasseh leads the people to do worse than the nations that preceded them in the region.
God Does Some Dishwashing
God sends a message through the prophets, telling the people that he's going to punish the nations for all these sins into which Manasseh has been leading them.
Manasseh, says God, is worse than the Amorites who came before him.
The same evil fate Ahab brought on Israel, Manasseh is now bringing on Jerusalem. God will wipe the city clean like a dirty dish, emptying it and sending the remaining remnant into exile, into the hands of enemies.
In addition to idolatry, Manasseh also kills plenty of innocent people in Jerusalem.
When Amon dies, his son (also Amon) takes over and leads the people in the same wicked deeds. He starts reigning when he's twenty-two years old, and reigns for two years.
A group of conspirators kill Amon Jr., but the people kill the conspirators too and make Amon's other son Josiah their new king.