"I don't deserve to be forgiven for something this bad"
How it sounds in your head: What you did is different. It's worse than what other people do. God forgives normal mistakes but this crossed a line. You used up your forgiveness quota. Real men face consequences.
"The blood of Jesus Christ His Son cleanses us from all sin."
-- 1 John 1:7Enemy creating tiers of sin to make the Cross insufficient for certain categories of failure.
His sin feels uniquely terrible in his mind, and he's been taught some things are unforgivable even if the church won't say it out loud.
Manasseh sacrificed HIS OWN CHILDREN to demons, filled Jerusalem with innocent blood, and practiced witchcraft for 55 years. When he repented, God IMMEDIATELY restored him and gave him back his kingdom—no probation period, no penance.
I REFUSE the lie that my sin is too big for the blood of Jesus. IT IS WRITTEN that His blood cleanses from ALL sin—not most, not small sins, not respectable sins—ALL. I am not special in my badness; I am covered by His goodness. IT IS WRITTEN in Psalm 103:12 that as far as the east is from the west, so far has He removed my transgressions from me. I receive the BARAK blessing that protected Judah even after he SLEPT WITH HIS DAUGHTER-IN-LAW thinking she was a prostitute—and he remained in the MESSIANIC LINE. The blood covers everything instantly.
Your Father isn't ranking your sins on a scale deciding which ones disqualify you—He's throwing a robe on you before you finish your apology speech. The thief on the cross was a violent criminal who did NOTHING to earn paradise, yet Jesus gave it to him in one sentence.