Infinite grace

For I am the least of the apostles, that I am not worthy to be called an apostle, because I persecuted the church of God. But by the grace of God I am what I am: and his grace which was bestowed upon me was not in vain; but I labored more abundantly than they all: Yet not I, but the grace of God which was with me.
I Corinthians 15:9, 10

The beauty of grace is that it doesn't just work for great people or even just pretty good people. It works for losers and screw-ups. God used Paul because, just like he says in the verse, he was simply unworthy to do anything of the sort. Paul hated God, hated the church, and killed hundreds of innocent people, and out of all the people in the world, God chose him. If anyone should have been damned by God right then and there, it was this man. That's the whole point! God's grace works for anyone because it's not about the capability of that person. "I labored more abundantly than all, but NOT I, but the grace of God which was with me."

It only makes sense that grace works for everyone, because it's all God's doing, and he never changes.