ARE THERE SINS THAT GOD CANNOT FORGIVE? By Robert Collins

First of all almost Every sin can be forgiven. Final impenitence is the refusal to ask for forgiveness, and certainly that can result in a person dieing in a state of mortal sin.
The Church’s understanding of suicide is:
2280 Everyone is responsible for his life before God who has given it to him. It is God who remains the sovereign Master of life. We are obliged to accept life gratefully and preserve it for his honor and the salvation of our souls. We are stewards, not owners, of the life God has entrusted to us. It is not ours to dispose of.
2281 Suicide contradicts the natural inclination of the human being to preserve and perpetuate his life. It is gravely contrary to the just love of self. It likewise offends love of neighbor because it unjustly breaks the ties of solidarity with family, nation, and other human societies to which we continue to have obligations. Suicide is contrary to love for the living God.
2282 If suicide is committed with the intention of setting an example, especially to the young, it also takes on the gravity of scandal. Voluntary co-operation in suicide is contrary to the moral law.
Grave psychological disturbances, anguish, or grave fear of hardship, suffering, or torture can diminish the responsibility of the one committing suicide.
2283 We should not despair of the eternal salvation of persons who have taken their own lives. By ways known to him alone, God can provide the opportunity for salutary repentance. The Church prays for persons who have taken their own lives.
The only sin that cannot be forgiven is believing that your sin is so great that not even God can forgive it. This is called the sin against the Holy Spirit. If we ask ourselves what is the greatest sin ever committed, we would all say the crucifixion of Jesus on the cross. Yet the first thing he said on the cross was, “Father forgive them, for they know not what they do.”
As to suicide, the story, born out by witnesses, goes that a woman whose son committed suicide by jumping off a bridge went to Padre Pio while Padre Pio was still living and was in a line of people waiting to see him. When Padre Pio walked by her, he stopped and said to her, before she had a chance to say anything to him, “Do not worry about your son, he repented between the bridge and the water.”
This simply shows the extent of God’s mercy for each of us. As is recorded in the diary of St Faustina Kawolska, Jesus said to her, that “I DESIRE MERCY, NOT JUSTICE.” Mercy is for the living, justice is for the dead.