12 Killers

Karla Leanne Homolka became one of Canada's most infamous female killers after participating in the murders of her younger sister, Tammy Homolka, Leslie Mahaffy, and Kristen French alongside her husband, Paul Bernardo, between 1990 and 1992. Initially portrayed as a battered spouse, Homolka secured a controversial plea agreement before investigators discovered videotapes documenting her active participation in the crimes. She served 12 years in prison and was released in 2005, making her one of the most controversial offenders in Canadian criminal history.