In 2 Samuel 11 , we see King David commit adultery and murder. Although we see in verse 27 of the same chapter that “the thing that David had done displeased the Lord”, we also see David referred to as a “man after God’s own heart” (I Samuel 13:14; Acts 13:22 ) and can observe his repentance of the sins he committed in Psalms 51.
In the New Testament, we see one of Jesus’ disciples, Peter, say he’d never deny Christ (Matt. 26:35 ) but he later went on to abandon Jesus in the garden of Gethsemane (Matt. 26:56 ) and deny Christ three times (Matt.26:69-75). Despite these shortcomings, Peter went on to be a powerful teacher preaching to believers scattered throughout the land (1&2 Peter).
We are given the example of Saul in the Bible in Acts chapters 7, 8 and 9. Saul (later called Paul) was one who had been involved in the persecution and murder of many faithful Christians but God went on to use him as one of His more earnest teachers. Paul went on to say in Romans 5:8 “But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us.”
If God can forgive adulterers, murders and more, He most certainly can forgive you. God does not want anyone to perish, but for all to come to repentance and be saved (I Peter 3:9, I Tim. 2:3-4). You need only hear (Romans 10:17 ), believe (Mark 16:16 ), repent (Acts 3:19 ), confess (Luke 12:8 ), and be baptized (Acts 2:38 ) and a Christian must also be willing to take up their cross and follow Him (Luke 9:23 ).