In the vast majority of times, when Mormons talk about forgiveness, it’s about their duty to forgive. It is not about God forgiving them. It is more burdensome law than uplifting gospel.
When Mormonism does talk about God’s forgiveness, it emphasizes that a person must earn God’s forgiveness. “Peace comes only through forgiveness. But forgiveness has a high price. Elder Kimball said: ‘To every forgiveness there is a condition. … The fasting, the prayers, the humility must be equal to or greater than the sin. There must be a broken heart and a contrite spirit. … There must be tears and genuine change of heart. There must be conviction of the sin, abandonment of the evil, confession of the error to properly constituted authorities of the Lord’” (Gospel Principles, p. 252).
Biblical Christianity teaches that God forgives us freely because Jesus has already paid the entire debt of our sin. See Hebrews 10:17-18.