5. Belle Gunness
Belle Gunness used to make a living by marriage. She used to marry people and take their lives to inherit their insurances.
She immigrated to the United States from Norway in 1881 and settled in Chicago. She married a Norwegian immigrant, had children with him, and then set him on fire in the store they has together. She claimed insurance money and got remarried, killing each of her husbands one by one.
She was a master tactician. Belle promoted herself in the press to attract male suitors and invited them to visit her farm in Indiana. Except for one guy who fled to recount his story, the suitors vanished into thin air after they visited Belle.