The Hotline Miami Add-on for PAYDAY 2 has 12 achievements.
In the Hotline Miami job, complete the heist while you and your four man crew are wearing one different Hotline Miami mask each on the Hard difficulty or above. Unlocks the "Silent Death" and "Folded Stock" for the Uzi submachine gun, "Suppressor" and "No Stock" for the Cobra submachine gun and "Short Barrel" for the Blaster 9mm submachine gun.