Madame Alexe Popova (1879-1909) murdered over 300 men over 30 years near her home in Samara, Russia. She may have taken her “cause” a wee bit far, but the purpose of her murder-for-hire business was to “free unhappy wives from their tyrant husbands.”
She charged small fees to women in Russia who were being abused or “held captive” by their cruel husbands- using mostly poison to carry out her work. Popova would become familiar with the victim and then slip him poisoned food or drink after gaining their trust. (After a few glasses of vodka, I’d trust anyone.)
Alexe was caught when a remorseful wife had second thoughts and reported it to the police. When captured, Popova made a full confession and never showed a bit of remorse- even appearing boastful about her good work. She also said she was justified for her actions and never killed a woman.
She was saved from an angry mob (of mostly men, I’m sure) but eventually executed by firing range in St. Petersburg.