What sect(s) teach that apostasy is unforgivable?

Imagine Bob. Bob was, at some point, Christian. Perhaps he was raised that way, or perhaps he came to faith later in life, but at some point, he was confirmed, communing regularly, professing Christ, and has felt God's Presence in his life. Then, something happened. Some event caused Bob to turn away from Christ to pursue a different path. Maybe the breakup was public, or maybe it was just in the privacy of his heart, but at minimum, Bob said to God, "go away; I don't need or want you". ---- A certain user cited Hebrews 6:4-6, claiming that Bob, having apostatized, can no longer be redeemed: > 4For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, 5And have tasted the good word of God, and the powers of the world to come, 6If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame. (KJV) However, this seems contrary not only to Scripture (with God, all things are possible), but to God's own nature (God is patient, wanting everyone to be saved). Indeed, most sects as far as I can tell teach that there is no sin from which one cannot repent, and that it is only by remaining in sin that one cuts *one's self* off from Salvation, essentially by refusing to accept the free gift. Logically, moreover, this teaching would suggest to Bob that God despises him and that not only should he not bother to seek God, he might as well do all he can to be God's enemy since he has nothing to lose. **Which sect(s) teach that one who has fallen off the path cannot be called back?**