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