The moment that you speak of, I believe, is the one which occurs when the other family members have been taken into the woods and killed by the criminals.
It is ironic that the grandmother is the last to die, as she is the one who truly creates the scenario in which the family is at the mercy of the Misfit.
As the grandmother becomes aware of her impending doom, she reaches out to the Misfit in the only way she knows how, through her religion:
"Jesus!" the old lady cried. "You've got good blood! I know you wouldn't shoot a lady! I know you come from nice people! Pray! Jesus, you ought not to shoot a lady. I'll give you all the money I've got!"
"Lady," The Misfit said, looking beyond her far into the woods, "there never was a body that give the undertaker a tip."
The Misfit has the callousness to rebuke even an older woman, one who has gotten by on her own form of southern charm.