9. Elizabeth Wettlaufer

Wettlaufer, 49, of Ontario, intentionally administered fatal doses of drugs to her victims, aged 75 to 96, between 2007 and 2014. After killing, she would post some of her dozens of verses. Wettlaufer's victims included five women and three men - all of whom were patients at Caressant Care nursing homes in Ontario, where Wettlaufer had worked.