[Nateman]

...God alone knows...

Isn't doing evil in the Lord's name the one sin that cannot be forgiven? Old Moe has got everybody beat without any close seconds.

[skr]

Matthew 12:31-32
“Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven. Whoever speaks a word against the Son of Man, it shall be forgiven him; but whoever speaks against the Holy Spirit, it shall not be forgiven him, either in this age or in the age to come.

Source: http://bible.knowing-jesus.com/topics/Unforgivable-Sin

[Arlis]

Personally, I believe the sin that cannot be forgiven is attributing to Satan the works of the Holy Spirit. In the context of what Jesus said, this is a reasonable conclusion.

To do so requires either deep and complete self-deception, or worse - doing so knowing that it is a lie.

[glennaro]

Hence, the unfortunate mis-translation from the original Hebrew of the Third Commandment to not misuse God's name, replacing "carry" with "take". "Take" has resulted in widespread misunderstanding of the Commandment. "Carry" is clear that "do not carry God's name in vain" clearly means do not do evil in God's name ... a sin only God could forgive, but He will not forgive.