I find it fascinating—and significant—that the apostle Paul so seldom uses the word “forgiveness” in his letters—never in those letters scholars consider to be authentically Pauline (except in an Old Testament quote) and very few times elsewhere.
I think the reason is that, for Paul, sin is primarily the condition of not being a Jew. He wrote in Galatians 2:15, We ourselves are Jews by birth and not Gentile sinners.
The burden of his theological thinking was to resolve the outsider status of Gentiles, to whom he felt sent. What is needed to alleviate this condition is not forgiveness, but a change of status, hence his choice of the word “justification” to indicate how the Gentile “sinner” becomes one of God’s people.