We have managed to play Prey a few hours before the game launches worldwide so we was able to dig through the game and help you out if you are having any trouble with the game.
How To Defeat V-122854-12
The best way to defeat this enemy is to use EMP’s and then slowing time to have more time to attack. It’s best to use the Shotgun if possible, but any weapon will work using this tactic.
How To Get A Shotgun
You will find a Shotgun in the mission “Detour” when you reach level 3 of the area “Arboretum” you should see it on the floor next to a dead person called Evelyn McCarthy. It is missable so make sure that you don’t run past the Shotgun.