"While Manasseh may have been an ungodly king in the beginning, he redeemed himself somewhat in the end. Manasseh reigned longer (55 years) than any other Israelite king and had the dubious distinction of being Judah's most wicked king. He came to the throne at the age of 12, although he probably co-reigned with Hezekiah for ten years. His father's godly influence appears to have affected Manasseh only negatively, and he reverted to the ways of his evil grandfather, Ahaz.

Committed to idolatry, Manasseh restored everything Hezekiah had abolished. Manasseh erected altars to Baal; he erected an image of Asherah in the Temple; he worshiped the sun, moon, and stars; he recognized the Ammonite god Molech and sacrificed his son to him, he approved divination; and he killed all who protested his evil actions.

Manasseh was temporarily deported to Babylon where he humbled himself before God in repentance. Upon Manasseh's return to Jerusalem, he tried to reverse the trends he had set; but his reforms were quickly reversed after his death by his wicked son Amon."
(from Nelson's Illustrated Bible Dictionary, Copyright (C) 1986, Thomas Nelson Publishers)

Contrast the above description of Manasseh to his grandson Josiah.

II Ki 23:25
Neither before nor after Josiah was there a king like him who turned to the LORD as he did-- with all his heart and with all his soul and with all his strength, in accordance with all the Law of Moses.

What a statement to Josiah’s character! Notice all the “all”s. 

We have reference to this commandment in the gospels.
Mark 12:30
and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength."  This is the first commandment.

However, even a godly person like Josiah can still suffer because of the sins of others.

II Ki 23:26
Nevertheless, the LORD did not turn away from the heat of his fierce anger, which burned against Judah because of all that Manasseh had done to provoke him to anger.

Sin has consequences. Sin is like an open wound. The wound may heal but often scars remain.