I believe that there is a forgiveness (remission) of sins that refers to being released from the "wages of sin" being "death." That release from death would require the reception of eternal life; and that of course, is a one-time transaction. Romans 6:23: "For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord." Ephesians 1:7 and Colossians 1:14 speak of a "redemption" (GK: apolutrosis) which is the remission of sins: "In Him we have redemption through His blood, the forgiveness of sins, according to the riches of His grace." That forgiveness is a one-time release from the wages of sin that necessitates regeneration, unlike other uses of forgiveness in Scripture that addresses the temporal consequences of sin. It's like where Jesus said, "He who is bathed needs only to wash his feet, but is completely clean; and you are clean, but not all of you." John 13:10
Why do we need eternal life? Sin
brought death. If I'm released from the wages of sin, then I must be
justified and given eternal life, or otherwise, I'm still under the wages
of sin, being death. This is how I understand forgiveness in
some of its usages.
Forgiveness in some Scriptures refer to this release from the wages of sin, which must result in eternal life, which is a one-time transaction. This forgiveness is a redemption that we receive in Christ, through his blood, such as we read in Ephesians 1:7 and Colossians 1:14: "in whom we have redemption [apolutrosis] through His blood, the forgiveness of sins." I believe this redemption which is the forgiveness of sins is being released from the wages of sin, and that requires the reception of eternal life, since death is the wages of sin. I believe Romans 6:23 speaks of this: "For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord."
Some references to forgiveness refer to being released from the
temporal consequences of sin, but the loss of eternal life is not in
view. I believe there's a one-time type of forgiveness which releases from
the eternal consequences of sin resulting in justification and regeneration,
otherwise, we are still dead, eternally speaking.
The death of Christ relates to releasing us from the consequences of sin, which is not just judicial forgiveness, but justification, regeneration, and existence in the kingdom and world to come.
I also believe Christ paid the debt in full, but the release from the debt is conditional, because the status of an individual doesn't change until they meet that condition. They are still unaccepted, alienated from God, and if they die that way, they go to the only place available to them, the "Lake of Fire."
Jesus
did the hard thing in that he met the righteous requirement for our sins to
God's righteous satisfaction. Now, the easy thing can be done in releasing us from that
obligation, but that release is made conditional by believing in Jesus for it. I
believe that release is forgiveness of sins, resulting in justification, regeneration, and
finally, glorification in the resurrection--all these solve the consequences
of sin.
When we sin as a believer, we must acknowledge it to be forgiven, but this is temporal forgiveness. If we don't acknowledge the sin, the consequence can continue, but with judicial forgiveness, the consequence is forever removed, otherwise, we would have to be justified and regenerated again after every sin. Judicial forgiveness is a one-time transaction at salvation, resulting in justification and regeneration. Fellowship forgiveness is not a one-time transaction.