"'Whoever blasphemes against the Holy Spirit never has forgivness, but is guilty of an eternal sin.' [Mk. 3:29; Mt. 12:32; Lk. 12:10] There are no limits to the mercy of God, but anyone who deliberately refuses to accept his mercy by repenting, rejects the forgiveness of his sins and the salvation offered by the Holy Spirit. [John Paul II, DeV 46] Such hardness of heart can lead to final impenitence and eternal loss."
There are six sins that offend the Holy Spirit. These are:
Despair, Presumption of God's mercy, Impugning the known truth, Envy the spiritual good of another, Obstinacy in sin, Final impenitence.
"Whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come." [Mt. 12:32]
"But whoever blasphemes against the Holy Spirit can never have forgiveness, but is guilty of an eternal sin." [Mk. 3:29]
"And everyone who speaks a word against the Son of Man will be forgiven; but whoever blasphemes against the Holy Spirit will not be forgiven." [Lk. 12:10]
All of which the RCC is guilty of.