The turning point for Bigger Thomas in Richard Wright's "Native Son" occurs when the family's apartment is invaded by a rat. It is a disgusting spectacle as Bigger attacks the pest with a frying pan: "...it reared once more and bared long yellow fangs, piping shrilly, belly quivering."
Bigger finishes the rat off by pounding in its head with a shoe. Bigger, in typical big brother fashion, scares his sister Vera with the disgusting remains. She faints, and his mother scolds him, "Bigger, sometimes I wonder why I birthed you." Bigger responds, "Maybe you oughtn't've."
The rat and his mother's response to him is the proverbial last straw for Bigger, whose poverty and reason for being alive are equally unknowable.