What are the sins that are unforgivable, even with repentance?
We are told anecdotally that sins are forgiven with repentance but nothing is defined as to what is a step too far, what sin is too grave or too mortal that it can't be forgiven because maybe the person knew what they were doing when they did it (taking advantage of God's Grace) eg. repeated sexual immorality and lusting? or perhaps, it was just too diabolical like murder, somebody might be taken by the devil spirit for a moment in anger and killed somebody in hate? If this evil person repented, would this be forgivable? Is there anything in scripture to support your view, sorry these examples are extreme but I suppose they would be extreme ones arguably.
To contextualize the protestants like the Calvinists believe that people are designated as the elect or the reprobates, just 2 groups. They believe that the elect have secured salvation and it can't be lost. And I suppose this question bears on Calvinism too but I'm just appealing to the catholic side.