Listen to Paul testify of his life before converting to Jesus as the Christ, 

“Indeed, I myself thought I must do many things contrary to the name of Jesus of Nazareth. This I also did in Jerusalem, and many of the saints I shut up in prison, having received authority from the chief priests; and when they were put to death, I cast my vote against them. And I punished them often in every synagogue and compelled them to blaspheme; and being exceedingly enraged against them, I persecuted them even to foreign cities” (Acts 26:9-11). 

He did whatever he could think of that was contrary to the name of Jesus of Nazareth. 
He put followers of Jesus in prison. 
He voted to put them to death. 
He punished them, and did whatever was necessary to make them blaspheme Jesus. 
He traveled to carry out his plans of persecution against the disciples of Jesus. 
 
Yet, when Paul saw the truth about Jesus of Nazareth, the man turned himself around completely and the Lord used him to write a major portion of the New Testament, which in turn has changed the world forever.