10. Dorothea Puente: Death House Landlady
This frail-looking woman is actually one killer landlady! Dorothea Puente ran a boarding house in Sacramento, California. Little did the people around her know that she was killing her mentally challenged boarders. And she was also cashing in their social security, to make money off them.
She was finally convicted for 9 murders and was sentenced to two life sentences for her heinous crimes. She dies in 2011 in a prison at the age of 82.