1. Thomas Cream
Thomas Neill Cream was a Scottish-Canadian doctor known as the "Lambeth Poisoner." In the 1890s, he poisoned and killed a number of his patients while working in Chicago. Despite being convicted of poisoning a woman and being given life in prison, he had his sentence commuted after his brother bribed the governor of Illinois.
He then travelled to London where he poisoned and killed five hookers before he was arrested and executed in 1892.