Here is the full list of all 18 One Shot achievements.
The base game contains 6 achievements, and there is 1 DLC pack containing 12 achievements.
Killed 10 Enemies.
Killed 500 enemies
Killed 1500 Enemies
Wasted your first bullet.
Got a score of 10,000
Got a score of 35,000!
Killed 5000 enemies!
Got a score of 1000!
Got a score of 5000!
Used slow-mo 10 times!
Used slow-mo a 100 times!
Used slow-mo 500 times!