bit necro, srry for that. I got the 20 kill archievement at the level where you penetrate one of the last bastions of the cult of shelgeroth, the one where you meet their turrets for the first time. The second to last room, the third door you need to open via a computer.
They waited for me (Commander Gabriel Da'vor), they heard our force gather in front of the door, the soft rambling of heavy armor and a pounding step of unseeable weight. When i gave the sign, my engineer Librarian Pavarthian touched the button, i myself got the fist step in, threw three grenades shortly after each other and swong my sword to cut down the nearest enemies. My soldiers Dalan Ortho, Brother Titus and Brother Hasta where only a split second behind me and shot down the remaining rebels to blood and dying breaths. Nyra secured my flank and the room was almost entirely clear, only a few cowards left in the corners of the room. After reloading, my squad dispatched of them quickly.