Who or what is the real monster in "A Good Man is Hard to Find"?I have to write a paper on this short story and the question is, My thoughts so far...

 Concerning "A Good Man is Hard to Find," first, we need
to clear up a misconception.  The Misfit doesn't say he's innocent, and the story
doesn't suggest that he is.  He says he can't remember doing what he's supposed to have
done.  That's not the same as being innocent.  And he certainly does not act innocently
in the story.  Though he is respectful, polite, and in a warped way considerate, he is
also self-centered, brutal, and destructive.  He has obviously done some thinking, but
his thinking in some ways is still extremely simplistic and warped.  He can certainly be
classified as a "monster," if that's what your assignment calls
for.

The story, however, is really about the grandmother. 
O'Connor believed that Christians like the grandmother are so lost and fallen that the
only way for them to be brought back to God's grace is an encounter with a devil-like
person.  She is egotistical, self-centered, selfish, ignorant, inconsiderate, dishonest,
and sneaky.  The way for her to be reformed is to encounter The Misfit.  Notice that her
epiphany, the moment she changes from the dogmatic and simplistic you should
pray, you should pray to you're a child of God thinking
isn't even when her family is taken off to be killed, but only when she is about to be
killed.  She is not a nice human being, to say the least, though I don't know if you'd
call her a monster. 

Whether or not her epiphany is genuine
or just another ploy to escape death is debatable, but The Misfit accepts it as
genuine.  If he is correct, then the grandmother is reformed by her encounter with the
"monster," though she is killed almost immediately after.