2 Chronicles - Chapter 33

Manassah was an evil King, and the description of his actions suggests that he is beyond forgiveness:

"Manasseh was twelve years old when he became king, and he reigned in Jerusalem for fifty-five years. He did evil in the eyes of the Lord, following the detestable practices of the nations the Lord had driven out before the Israelites. He rebuilt the high places his father Hezekiah had demolished; he also erected altars to the Baals and made Asherah poles. He bowed down to all the starry hosts and worshipped them. He built altars in the temple of the Lord, of which the Lord had said, ‘My Name will remain in Jerusalem for ever.’ In both courts of the temple of the Lord, he built altars to all the starry hosts. He sacrificed his children in the fire in the Valley of Ben Hinnom, practised divination and witchcraft, sought omens, and consulted mediums and spiritists. He did much evil in the eyes of the Lord, arousing his anger."

However, when Manassah was taken captive to Babylon, he turned to God:

"In his distress he sought the favour of the Lord his God and humbled himself greatly before the God of his ancestors. And when he prayed to him, the Lord was moved by his entreaty and listened to his plea; so he brought him back to Jerusalem and to his kingdom. Then Manasseh knew that the Lord is God."

Jesus told a parable (in Luke 15) of the lost son, who also turned against his father, and squandered his inheritance.  He thought that he was no longer worthy to be called a son.  However, when he returned to his father, he was restored to his rightful place as heir in his home.

The illustration of God's forgiveness for a son was demonstrated in his response to King Manassah.