Destiny Eris Morn Bounty EXTERMINATION
During the Dark Below Quest SIEGE OF THE WARMIND, you will have to enter Bunker Ras-2. You will find 3 Knights down there. Kill all 3 and let yourself die so you can do it again. The respawn point is directly before this section, so you can get the 25 kill for the Exterminator bounty very quickly.