Question: Is there any sin God won't forgive?

Answer: God has shown Himself throughout Scriptures as being merciful and forgiving. If anyone would repent (turn away from his sin) and seek God's forgiveness, He would forgive (see Acts 3:19, 1 John 1:9-10, 2 Chronicles 7:14) -- regardless of the sin (or amount of them). Yet Jesus spoke of one sin that was different than all the rest... Matthew 12:31-32 "Therefore I say to you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven men. (32) Anyone who speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age or in the age to come." (NKJ) Blasphemy of the Holy Spirit is obviously not something committed by even Saul of Tarsus -- who arrested, imprisoned and railed against Christians and Jesus Christ (Acts 9:1-2). He had even participated in the murder of one person (Acts 8:1). God not only forgave him all that but used him for the rest of his life (Acts 9:15). Looking at the task of the Holy Spirit, it gives insight into what would be blasphemy of Him... He dwells in believers forever (John 14:16-17). He teaches us of Jesus (John 14:26, 15:26) He guides us into all Truth (John 16:13) He convicts of sin (John 16:7-8) To die having rejecting the message of the Holy Spirit -- the message to repent of sin and find salvation in Jesus Christ -- is to blaspheme Him. Dying in rejection of His message is to have spoken against Him, this is something that is irreversible and unforgivable (Hebrews 9:27, Revelation 20:11-15). While you live it's not to late.