Here is the Reverend Billy Graham giving a sermon about forgiveness. 

This is a discussion that mentions The Holy Bible's description of the case of King Manasseh who had re-instituted Baal worship and other pagan human sacrifical religious practices and caused much bloodshed in Israel.  Manasseh also was resposible for the death of the Prophet Isaiah. 

Yet, Billy Graham said here in this sermon, yet God forgave Mannasseh nonetheless when Mannasseh had a true change of heart, and asked for mercy from God.