Manasseh was the evilest king that ever reigned over God's people. Idolatrous, blasphemous, cruel.
But the Lord would not relent.
Because of His love for Manasseh, God gave him over for a time to his enemy. It was there the miraculous happened. And when he was in distress, he entreated the favor of the Lord his God and humbled himself greatly before the God of his fathers. Then Manasseh knew that the Lord was God. 2 Chronicles 33:12-13
Manasseh knew the Lord.
He was saved.
He was redeemed.
God's grace is fierce.
The blood of the Lamb brings deliverance. Redemption is possible until the final breath. Never give up on that one you're praying for.