Manasseh was twelve years old when he became king, and he reigned fifty-five years in Jerusalem. But he did evil in the sight of the LORD… 2 Chronicles 33:1-2
Now when he was in affliction, he implored the LORD his God, and humbled himself greatly before the God of his fathers, and prayed to Him; and He received his entreaty… Then Manasseh knew that the LORD was God. (v.12-13)
So Manasseh rested with his fathers, and they buried him in his own house. Then his son Amon reigned in his place… But he did evil in the sight of the LORD, as his father Manasseh had done… (v.20-22)

Manasseh was the worst of the Kings of Judah, sinning more than the pagans displaced by Israel when they entered the Land under Joshua.

God turned Manasseh over to the Assyrians, who took him as a prisoner to Babylon. While there, Manasseh repented. God brought him back to Jerusalem, where he sought to make reforms. But the people were so entrenched in their wickedness, they did not follow the king’s good example as they had followed his bad example.

When Manasseh died, his son, Amon, became king. Amon followed his father’s example in sin, but not in repentance. He was assassinated after ruling only two years. Lessons to learn?

Even the worst sinner can be saved and repent.
While sins of the repentant are forgiven, the damage done by past sin may still have lasting consequences.
Parents’ repentance does not guarantee repentance by our offspring.

Overall, God is incredibly gracious, but sin is not without consequences.