Madame Defarge has lived her life witnessing and experiencing the horrors that the French aristocracy inflicts on the peasant class. She sees them as a part of society that should be completely and violently abolished in order to make way for a more just and egalitarian nation.
However, her lust for the destruction of the aristocracy is more than simple ideology. She has a personal score to settle. Near the end of the story, we learn more about her traumatic backstory. It turns out that French aristocrats, namely the Evremonde brothers, are responsible for the destruction of her entire family. When she was young, the Evremondes raped her sister, which ultimately resulted in the death of the sister, her sister's unborn child, her father, her brother, and her brother-in-law.
Madame Defarge dedicated her life to vengeance. However, she does not just want the Evremonde bloodline, which includes Charles Darnay, forever wiped out; she wants the entire system that allowed for such oppression...
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