It is a bit difficult to find a name with this description. Not impossible, but the question is if a name fitting that description would be justified. Which leads to the question if your game is actually more in-depth in terms of mechanics or lore - or not.
Because if you have a deeper story to tell, or an emphasis on the character, their behaviour or twists in gameplay - or the gameplay itself has an interesting mechanic or engagement with the world - it becomes interesting to think about how to integrate this into the name to reflect that.
If none of the above is the case and you want to make a simple FPS, than a simpler name is of course fitting enough. You could still call it like the character, or the enemy species, or the world, or take the route of 'The game is grim and has a harsh environment - so we can give it a dark or hopeless name'. Or just something bombastic that says 'action!'.
Going from all that, whatever the name is: Make a google search and see if the name is already used somewhere. If yes, maybe you have an alternative that gives the point across the same way - or something else that would fit?