Unbelief is sin...1 John 3:23.Its what gets you thrown in hell so why dont you tell us.
Sin is what separates an individual from God...Isaiah 59:2.
If someone is in a state of unbelief, they aren't placed under condemnation. They are already under condemnation...John 3:18.
If unbelief is a sin, it can be forgiven. Anyone who believes was once in unbelief.
On the cross, our sins were bore in Jesus body. If this is so, then according to many here, God, having paid for every sin of every person, is now acting unrighteously by still requiring sins to be paid for that have been placed behind His back and remembered no more.