“What did Paul mean when he said he was the chief of sinners?”
“…Christ Jesus came into the world to save sinners; of whom I am chief” (1 Tim. 1:15)
When we think of sinners, we generally think of those who commit carnal, fleshly sins such as fornication and murder. But the Bible speaks of another kind of sin, that of religious pride and hypocritical self-righteousness. You’d think God would hate fleshly sins more, but when the Lord was here, He was kind and patient to sinners of that genre. By contrast, He delivered blistering denunciations of the scribes and Pharisees for their religious pride and self-righteousness, and for their persecution of their Messiah.
But it doesn’t really matter which sort of sin is worse in the context of this question, for before he was saved, Paul was guilty of both varieties. Murder is the worst sort of fleshly sins, and he was guilty of murdering God’s people. But he persecuted them in religious self-righteousness, for “touching the righteousness which is in the law” he was “blameless” (Phil. 3:6). This sinful combination certainly made him the chief of sinners.
In addition, the Bible word “chief” can mean most prominent, as it does when it speaks of “the chief singer” (Hab. 3:19) and “chief priests” (Ezra 10:5). The word can also have the idea of leadership. “The chief man” on the island where Paul was shipwrecked (Acts 28:7) was probably the leader of those native people, and “Beelzebub the chief of devils” (Luke 11:15) was a reference to Satan, who is certainly the leader of all devils.
So in calling himself the chief of sinners, Paul was also saying that he was the most prominent leader of the world’s sinful rebellion against God (Acts 8:3; 9:1). That’s why God saved him, to prominently show His grace in him (1 Tim. 1:16), just as He judged Pharaoh, the world’s most prominent and powerful leader, to show His power in him (Exod. 9:16).
This might be why Paul used the present tense to say he was still the chief of sinners, even now that he was saved. He was still the world’s most prominent example of the worst kinds of sinner saved by grace. source