Here is the full list of all 37 Alien Robot Monsters achievements.
Deploy 128 reinforcements
Fire 500 missiles from orbit
Gain all 111 stars
Complete all Planet X levels
Defeat final boss
Gain 90 stars
Gain 75 stars
Defeat Mountain biome boss
Defeat Swamp biome boss
Instakill 50 robots
Gain 50 stars
Save the natives
Build 800 towers
Deploy 32 reinforcements
Gain 40 stars
Build 400 towers
Defeat Wasteland biome boss
Field 256 marines
Destroy 128 robots with fire
Gain 30 stars
Build 200 towers
Destroy 100 robots in melee
Destroy 128 robots with Atomizer
Destroy 50 robots in melee
Field 64 marines
Destroy 99 robots with satellites
Defeat Forest biome boss
Use 1337 hand grenades or mortar rounds
Destroy 100 robots with snipers
Fire 256 sniper rounds
Build 50 towers
Destroy a robot with native arrows
Gain 10 stars
Gain 20 stars
Stun 384 robots
Field some space marines
Start your colonization of Planet X