In order to get the Hidden Achievement titled "Dev Killer", you need to beat the game. After the final boss, Dave will be taken to space, where you can fly around shooting aliens and Dev names. You must shoot all the Dev's names before time runs out (I barely made it in time!) while avoiding aliens.
Try not to worry about aliens too much unless you have to, as being hit will stun you, and you barely get enough time as it is. Also, this weapon can be rapid fired, so you don't have to aim again after every shot. Some of the Devs take way more damage than others, so make sure that you are using rapid fire.
In case you don't get the achievement because you ran out of time after beating the game (like I did), you can access the credits at any time while on the boat by bringing up the Phone Menu and choosing Minigames, and then Space Diver. So, don't feel worried if you don't get it on your first try also! This was the last achievement I got to get my 100% complete for this amazing game!
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