Ahaziah was crowned king after his father Ahab was slain in battle in a war against Syria (1 Kings 22:40). He was also a wicked king who worshipped Baal (Baal-zebub) (2 Kings 1:2).
Elijah also went into his court and pronounced judgments upon him (2 Kings 1:4). Ahaziah sent soldiers to Elijah three times trying to apprehend him, and each time Elijah caused fire from heaven to consume them. That story and all of the reign of Ahaziah is in 2 Kings 1.
His son Jehoram became king after his father's death.