No one goes to hell because he slips up. Slipping up is not a mortal sin. If you commit mortal sin, you know it, because you possess full knowledge and you did it with a deliberate act of the will.that’s why I think it is unfair. A man can lead a good life for eighty years or so, and then slip up at the last moment by not attending a Catholic Mass on Sunday and be condemned for all eternity to hell. But the other man who is bad for his entire life was lucky to have met up with a priest one hour before his execution, and he got to confess the thousands of times he caused horrific and unspeakable pain and hurt to others. And he is only sorry because he knows he will go to hell. So he ends up in heaven with all the angels and Saints.
If the hypothetical person “lived a good life” for 80 years and all of a sudden one day decides that he’s tired of the Church’s requirement and will not attend Mass anymore on Sunday and the Church be damned is deliberately turning his back on God and intentionally rejects him. God never forces his grace on anyone. So your hypothetical person knows that it’s a mortal sin and does it anyway, he is willingly choosing hell. There’s nothing unfair about that, since he himself wanted it.
This is because apart from God we can do NOTHING. Our good works are worthless. One thing Christians should always remember that we are NOT SAVED BY WORKS! Our good works are efficacious only when we are in a state of Grace. When a person leaves a state of grace through mortal sin, he cannot merit anyting. Only through the Cross can our works merit anything. So for one in mortal sin, his 80 years of good works are worth nothing.
And yes, if the criminal you mentioned truly repented of his lifetime of sin, offers up his execution as a just temporal punishment and turns to Christ for forgiveness, will indeed get his sins blotted out and he goes to heaven, perhaps with a stop in purgatory. All it takes is one confession: “I raped and murdered a thousand women. I am truly sorry and I ask God and men to forgive me. May God accept my death as a small atonement for my many grave sins, and may he have mercy on me a sinner.”
There is more rejoicing in heaven over this one repentant sinner. God is good.
Don’t try to ask for “fairness” from God, because if God were “fair”, we’d ALL end up in hell. You just be thankful he offers grace before judgment.