Final answer:
Paul felt he was the least of the apostles and not worthy to be called an apostle due to his previous persecution of Christians, but he recognized the depth of God's grace and forgiveness.
Step-by-step explanation:
Paul felt he was the least of the apostles and not worthy to be called an apostle due to his previous persecution of Christians. Before his conversion, Paul, then known as Saul, actively persecuted and arrested Christians. However, after his conversion, he realized the depth of God's grace and forgiveness and recognized that he had been chosen by God to spread the message of Jesus Christ.