Amy Archer-Gilligan
"Sister" Amy Duggan Archer-Gilligan (1868–1962) was a Windsor, Connecticut nursing home proprietor and multiple murderer. She systematically murdered at least five people by poison; one was her second husband, Michael Gilligan, and the rest were residents of her nursing home. It is possible that she was involved in more deaths; authorities found 48 deaths total from her nursing homes.
Read more about Amy Archer-Gilligan: Childhood and Marriage, Killings and Capture, Trials, Death, Publicity