What you are really asking is "what is the unpardonable sin?"...right?
If you look up in a concordance the phrase "unpardonable sin", you will find that in a few sentences before that one, there will be something to the effect that God will forgive EVERY sin...IOWs, there is no sin that God will never forgive... So, if you curse God, and then say youre sorry, God forgives...If you damn the Holy Spirit, He still forgives...
Shoot someone, God still forgives...
But there is one sin that is unpardonable....And that is the sin of never opening your heart and turning to God. If you never sought God, or worse, sought and rejected Him, thinking that He wasn't worth your time, and you never prayed to Him, that is the one sin He could never forgive, because you never asked Him to take you back. And that is the unpardonable sin....