What is the significance of the ending of Flannery O'Connor's "A Good Man is Hard to Find"?

At the end of the story, when the grandmother finally realizes what is happening, she begins to beg The Misfit to pray so that Jesus will help him. Right before The Misfit kills her, The Grandmother calls him one of her own children, recognizing him as a fellow human capable of being saved by God's Grace. Even though he murders her, the Misfit is implied to have achieved some level of Grace as well when he ends the story by saying, "It's no real pleasure in life." Earlier in the story, he claimed the only pleasure in life was meanness.