Eliyahu's mission to avenge the sinful kingdom of Israel and the House of Ahav by appointing Hazael as King of Aram, Yehu as King of Israel is not preformed by him, but by Elisha who is also part of this mission. Elisha instigates Hazael's reign in this chapter, but his character is a non-vindictive figure. Elisha's role is to mitigate the force of Aram and to ultimately prophesy the reversal of the tables in favor of Israel. 

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion