Flannery O’Connor's story “A Good Man is Hard to Find” uses The Misfit as an agent of change. How does The Misfit as an agent of change in the story for the other characters, and why is he qualified to make that change?

The Misfit acts an agent of change because he shocks the grandmother out of her complacency. He murders her entire family, and it is clear that he is about to murder her. All of a sudden, everything she has relied on to keep her safe has no value. She has been proud of being a lady, but when she uses that status to appeal to The Misfit, she realizes it has no value to him. She also relies on her money, but that too fails her, as The Misfit has no interest in a bribe.
As she faces death, the grandmother is stripped down to her essentials. She has nothing to rely on but God, and in this moment, God's grace pours down on her, allowing her to love The Misfit as one of her own children just as he is about to kill her.
The Misfit is not really qualified to make a change in the grandmother. Only God's grace can do that. But The Misfit becomes the catalyst or agent of her change by stripping away her props and forcing her to confront reality.