The case of the thief on the cross with Christ tells us how merciful God is.
Our Lord Jesus was placed between two thieves when He was crucified, the two of them were guilty as charged, but only of them choose to ask Him for forgiveness with humility.
The thief recognize that he was a sinner, so said he to Jesus," Lord, remember me when thou comest into the kingdom".
Jesus' reply that "Today you will be with me in paradise" tell us that we do not earn salvation by how much kindness we have shown to others but we gain it by faith and a sincere heart.
God's mercy is there for everyone who comes to Him with a genuine heart, and it does not matter how far the person has gone.