1800's woman who made a habit of eliminating people with arsenic who were insured or became an inconvenience.
I saw a good PBS film about the case.
Money was tight and there were few or no opportunities for a more comfortable economic situation. Once she collected life insurance money after a husband died, she sought to repeatedly resolve her financial difficulties with murder.
Later, murder became too easy for her. She began to kill those who were a burden to her.
When she got lucky and married a middle-class widower with children, his children began to die. There was no financial reason for these killings. She seemed to not be able to control her deadly desire.
She also could not control her spending once she had more money through this marriage, which strained the relationship.
After each marriage, money troubles soon returned, and her solution was to find another husband.