In "A Good Man is Hard to Find," the ending of the story establishes that the grandmother undergoes an epiphany, and that The Misfit considers that epiphany to be genuine. The story is about the grandmother much more than it is about The Misfit.
O'Connor believed that people are in such a bad way, spiritually speaking, that only an encounter with the depraved and grotesque canshock them into an awakening and rebirth. The Misfit is the depraved and grotesque, and the grandmother undergoes a spiritual rebirth due to his influence. The grandmother, accepting of almost no one and nothing throughout the story, accepts even The Misfit as a child of God when she experiences a real fear of death.
The grandmother is such a despicable person that the deaths of her family members do not lead to this epiphany. Only her own impending death triggers her new understanding. Nevertheless, God's grace does act on her as a result of her encounter with The Misfit. The ending demonstrates that even a person such as the grandmother can be changed by God's grace, according to O'Connor's beliefs.