One thing that struck me was his repetition of the belief that any sin can be forgiven. Any sin. Any. “There is no sin that can’t be forgiven,” he repeated over and over. And I thought about murder. About the premeditated taking of a life. About callously killing someone. I thought about terrorists, murderers, drunk drivers, mass shooters. Then I thought about God forgiving the sins of those people and I couldn’t wrap my head around it. Even if those people lay themselves in front of the altar and begged forgiveness, how can God say, yes, I forgive you? Any sin can be forgiven. Any sin.
on forgiveness and the church
Michele Catalano

Wouldn’t life be hopeless if it was possible to commit a sin that was truly unforgivable? Why continue to live in that case?

According to the Catechism of the Catholic Church, forgiveness requires a few things (my summary):

  1. Contrition. You must be truly sorry for your sins. This is an interior disposition that ultimately only God can measure. A priest in the sacrament of Confession can refuse absolution if he doesn’t sense contrition in the penitent. Perfect contrition is sorrow for offending God, not simply for getting caught.
  2. A firm purpose of amendment. Your confession isn’t efficacious if you don’t earnestly promise to avoid sin in the future. Conversion.
  3. Reparation. Forgiveness of sin doesn’t remove the damage done or the necessity to repair the damage. A murderer can be forgiven by God but still must suffer the temporal punishment of prison (or whatever legal measures). Some reparation can be performed in this life (e.g., paying my neighbor for a broken window) some only after death (the doctrine of purgation, Purgatory).
Then what’s to stop a person who believes in that next life, in passing through to the pearly gates and living amongst saints and people who have led virtuous lives or at least sinned to lesser degrees — what’s to stop someone with murderous intentions follow through on them if they think they’ll ask for forgiveness, get it, and still get to heaven?

This is the definition of severe sin, the active turning away from God. You’re not responsible for sins that you aren’t aware of but on the other hand, committing a sin with full knowledge that it’s a sin and doing it anyway… that can take a minor (venial) sin and make it mortal. To put it another way this is presuming God’s mercy.

And what is hell for? Is that for people who commit sins but don’t ask for forgiveness?

Presisely. God’s mercy is unlimited and freely offered but must be accepted. Acceptance requires conversion from sin.

What about people who don’t ask for forgiveness but are given it anyway by family members of their victims? Do they get a pass?

God offers us mercy and so calls us to offer the same mercy to those have hurt us. “Forgive us our trespasses as we forgive those who have tresspassed against us.” As Christians we are to offer forgiveness even if the person who hurt us hasn’t asked for it or even apologized. Being forgiven by the family of their victims doesn’t give the murderer a pass or at all change that person’s relationship with God or responsibility to repent and repair.

Truly there is only one unforgivable sin: refusing to accept God’s mercy. If you don’t accept mercy, you can’t receive it.