Jehu, the son of Jehoshaphat, was the tenth King of the northern kingdom of Israel. Jehu killed a great number of people. He killed the king of Israel, Joram, who was the son of Ahab, with an arrow through the heart. He also killed the king of Judah, Ahaziah. Joram and Ahaziah were related to each other through Ahab and Jezebel. In time, Jehu executed Ahab's entire family, including Jezebel, and fulfilled a prophecy of Elijah (1 Kings 21:17-24). Jehu also killed Ahab's friends and officials.
Aside from killing members of Ahab's family, who had encouraged the people to worship false idols, Jehu ordered his men to kill the priests of the pagan god, Baal, in a temple. He then converted the pagan temple into a public toilet.
Jehu reigned as king of Israel for 28 years. When he died, he was buried in Samaria, and his son Jehoahaz became the new king. The story of Jehu is found in 2 Kings, chapters 9 and 10.
In the British Museum, there is a limestone monument called "the Black Obelisk of Shalmaneser 3" (9th century BC). It depicts Jehu presenting tribute to the king of Assyria, and is the only likeness known of any King of Israel or Judah. In the Israel Museum there is a seal impression from Lacish with Jehu's name on it. The name Jehu means "Yahweh is He."
Next person in the Bible: Jekoliah (or Jecholiah, or Jecoliah)