King of Judea who ordered the Massacre of the Innocents (5)
I believe the answer is:
herod
(Other definitions for herod that I've seen before include "King of Judea in the time of Jesus" , "Biblical king of Judaea" , "King of Judea who ordered the death of children under two in Bethlehem" , "Infanticidal king" , "Cruel king" .)