The ransom paid by Jesus Christ, through His suffering in Gethsemane and His death on the cross, which nullifies the effects of sin. Christ’s atonement allows everyone to be resurrected. For those who repent of their sins, it also opens the way to continued growth and progression through the eternities.
In the video below, apostles in The Church of Jesus Christ of Latter-day Saints talk about how Christ's atonement can heal, change, and purify.