What sinS?
I've only found ONE.
Blasphemy of the Holy Spirit
Google unforgivable sin
Matthew 12:31-32
31 And so I tell you, every kind of sin and slander can be forgiven, but blasphemy against the Spirit will not be forgiven. 32 Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.
And the explanation of this Sin and why it can’t be forgiven
http://www.catholicculture.org/culture/library/view.cfm?recnum=6207
by Fr. Raymond Stoll, S.T.D.
Basically, this is a sin that the sinner can’t repent of, in short