Ninja Killer Achievement in Doom 3: BFG Edition
Kill 5 enemy players while using Invisibility in DOOM 3 Multiplayer
How to unlock Ninja Killer
For this achievement, you must eliminate five enemy players while you are under the effects of the Invisibility powerup. This does not have to be five different players and can be done on the same person five times.
Refer to the roadmap for the best and quickest way to boost all the online achievements and refer to step four of the roadmap to find partners for boosting them online.