In order to unlock this achievement, you must collect all the Doom dolls. (2 in each level) An awesome gamer over at TrueAchievements named Zasta 360GameTV made a complete guide that can be found here
TrueAchievements and deserves any and all credit for their great work! The playlist for all of his videos is in this link,
https://www.youtube.com/playlist?list=PLuGZAFj5iqHeHs_9TXd7o... , and I will go ahead and copy over his videos in order.
Mission 1Mission 2Mission 3Mission 4Mission 5Mission 6Mission 7Mission 8Mission 9Mission 10Mission 11Mission 12Mission 13So as I have said, please ensure Zasta 360GameTV ensures credit. As they most certainly deserve it!