Here is the full list of all 19 Action Alien achievements.
Kill 10 000 aliens.
Earn a total of 10 000 credits.
Unlock all golden weapons.
Unlock all upgraded weapons.
Beat 100 aliens with leg kicks.
Complete the petrol station map.
Demolish a part of a building with the grenade launcher.
Complete the tropical hotel map.
Use every weapon during one game.
Blow up 500 aliens with grenades.
Unlock all perks.
Kill 15 boss aliens.
Complete the wasteland map.
Kill 1 000 aliens.
Kill an alien boss with the pistol.
Empty all the rounds of a revolver with only deadly shots in less than 5 seconds.
Blow up 8 aliens with one grenade.
Kill 100 aliens.
Kill an alien with the last bullet of a machine gun or an assault rifle.