Well look at some examples in the Bible like saul who became Paul in the book of acts...before he was a christian he persecuted believers and was a self righteous Pharisee but after his encounter with Jesus he was nothing but kind to them and then went and told more and even welcomed gentiles to be believers. That was a complete turnaround. He was also willing to endure suffering and humiliation to spread the gospel, he was beaten up, put in prison, had to deal with false accusers, all the stuff that he was doing to to others before he came to the Lord.