According to Jesus, you can be forgiven all kinds of sin and blasphemy, except for one: blasphemy against the Holy Ghost.
Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men. And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come. Matthew 12:31-32
But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation. Mark 3:29
But unto him that blasphemeth against the Holy Ghost it shall not be forgiven. Luke 12:10
Those who deny Jesus will be denied by Jesus. (Which implies Jesus will never forgive them for denying him.)
Whosoever shall deny me before men, him will I also deny before my Father which is in heaven.Matthew 10:33
According to these verses, believers can be forgiven all things.
Through his name whosoever believeth in him shall receive remission of sins. Acts 10:43
And by him all that believe are justified from all things. Acts 13:39
And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses. Colossians 2:13
The great God and our Saviour Jesus Christ; Who gave himself for us, that he might redeem us from all iniquity. Titus 2:13-14
If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. 1 John 1:9