Here is the full list of all 15 Darkness Assault achievements.
Kill your first enemy
Make first shot
Die 1 time
Read any document through game menu
Launch game with Ultra Quality
Kill 5 enemies
Kill 25 enemies
Die 10 times
Die 25 times
Find S&W Model 625 MG
Find Glock 20
Find Beretta 92
Make 50 shots
Make 200 shots
Make 500 shots