Dhu Nuwas
When Dhu Nuwas invaded, he called upon its people to abandon Christianity and embrace Judaism. When they refused, he had them thrown into burning ditches alive. Estimates of the death toll from this event range up to 20,000 in some sources. Some sources say that Dus Dhu Tha'laban from the Saba tribe was the only man able to escape the massacre of Najran, who fled to Constantinople to seek help and promptly reported everything.