This kill bonus requires you to kill someone that is under the effect of the Cloak ability. This kill bonus varies according to whether you can see through the Cloak Ability. Insterestingly, CPU AI cannot score this achievement unless by pure luck or dumb actions (i.e. jumping into a 3-team close combat fight when you're on team 4, but you are cloaked), because they choose not to see people who are cloaked. This achievement can be attained in Level 9 Human Campaign as the aliens will be using cloaking technology the first time. Of course, Quickmatch at the Headquarteers with Deathmatch max players is ideal for getting this. Don't forget to make it Very Easy.