Here is the full list of all 10 GunSpectre achievements.
Complete the tutorial area.
Obtain a data crystal.
Obtain half of the data crystals.
Obtain all of the data crystals.
Eliminate 100 enemies.
Talk to every citizen of the wasteland.
Completely chart the surface and subsurface maps.
Eliminate all of the sub-bosses.
Beat GunSpectre in two hours or less.
Beat GunSpectre in any amount of time.