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