Recent talk by Dr. Stephen Chan, he mentioned the killing of 75,000, which is far greater than Bloody Mary's 300 top.
If it is true, what Esther did in a few days would be comparable to King Henry VIII's lifetime of slaughter.
However, I must note two things:
1. Matthew Henry was right when he said that Esther's slaughter was not against the innocents or civil rebels but against the foes that sought the lives of the Jews. It would equivalent to that of the casualties of a war. And by God's providence, out of fear, the foes have surrendered their lives to the Jews.
2. There are different prescriptions to the number being slaughtered. Septuagint has 15,000 while the Targums read 10,107. Also, the word אלף (thousand) could be read as family, clan.