Instructions
Trophy and Announcement
Begin a multiplayer match in "Halo 1," "Halo 2," "Halo 3" or "Halo: Reach." The trophy is only awarded in "Halo 3" and "Halo: Reach," but a Killjoy announcement will be made in "Halo 1" or "Halo 2" when you accomplish the task.
Wait for a player to go on a killing spree. Killing sprees are awarded after a player has killed five players in a row without dying herself.
Kill the player who is on the killing spree. A Killjoy is awarded when you stop another player's killing spree.
Killjoy Achievement in "Halo Wars"
Begin a skirmish or multiplayer match in "Halo Wars." The "Killjoy" achievement is awarded to a player who disrupts a leader's power. You can do this by using disruption bombs, which may be dropped by UNSC leaders.
Gain at least 450 supplies by building up your base.
Drop a disruption bomb on an opposing leader to disrupt her active powers. To drop a bomb, select the ability from the Spirit of Fire and then pick a location to bomb. Disruption bombs are considered a leader's power even though they are deployed through the Spirit of Fire.
Disrupt a leader five times in one game to get the Killjoy achievement.