Ranavalona I, also know as Ranavalo-Manjaka I, was a sovereign of the Kingdom of Madagascar from 1828 to 1861.
Although there are stories of her executing her own people (by boiling them and throwing their bodies off a cliff) for appearing in her dreams, I find the most fascinating controversy of her reign to be the Tangena ordeal.
One of the many brutal ways she maintained order within her Queendom was through the practice of "trial by tangena" Tangena is a poison extracted from a nut. It was ingested by the person on trial, with the outcome determining innocence or guilt. If you were to throw it up, you were innocent, if you died... well, guilty as charged.
Through slavery and torture, she killed off about 1/3 of her people.