Mormons often refer to Jesus as their Savior. They believe he paid their debt to Heavenly Father and also conquered death for them. But they also believe they have to pay him back in full (For a good example, see Boyd K. Packer’s parable of the debtor on lds.org.). In other words, they believe Jesus saved them by assuming their loan, refinancing it, and spreading out the payments. They do not believe he saved them fully and freely by paying for their sins and then canceling the debt.
Biblical Christianity teaches that Jesus is our Savior by being our *substitute* instead of our *example*. Jesus paid for our sins and doesn’t ask to be repaid. We receive the benefits of his salvation only through faith.