The saying is faithful and worthy of all acceptance, that Christ Jesus came into the world to save sinners; of whom I am chief.
Was Paul really the worst sinner of all time (cf. 1 Corinthians 15:9; Ephesians 3:8)? Obviously many people have lived longer in a more depraved condition than Paul did. He became a Christian relatively early in his adult life. Perhaps the apostle meant that he was the "foremost" sinner in the sense that his sin of aggressively tearing down the work that God was building up was the worst kind of sin. It was much worse than simply ignoring God and going one’s own way.