2 Kings 21:2, 9, 16 And he did that which was evil in the sight of the Lord, after the abominations of the heathen, whom the Lord cast out before the children of Israel….But they hearkened not: and Manasseh seduced them to do more evil than did the nations whom the Lord destroyed before the children of Israel….Moreover Manasseh shed innocent blood, till he had filled Jerusalem from one end to another; beside his sin wherewith he made Judah to sin, in doing that was evil in the sight of the Lord.
Manasseh was arguably the most evil of all the kings of Israel and Judah. And it gives one pause when remembering that he was the son of Hezekiah, the best king. He did more evil even than the pagan peoples the Lord rooted out. Not only did he do evil with his idolatry, but he also led the people of Judah to sin.
His atrocities were exemplified by two things he did: 1) he sacrificed his son to pagan gods, and, 2) he shed innocent blood, and tradition says that he had Isaiah the prophet sawn asunder (Hebrews 11:37).
It is hard to imagine a more evil person. However, it demands the belief that I, yes even I, am capable of the same wickedness, but for the grace of God. So I turn to the Lord always.