Here is the full list of all 30 In Game Adventure: Legend of Monsters achievements.
Get an Automatic Shotgun
Get a Machine Gun .50
Get an Rifle
Get an UZI
Get a laser weapon
Get a lance grenades
Get a rocket launcher
Unlock 10 weapons
Unlock the mountain area
Unlock the jungle area!
Unlock the dungeon area!
Unlock the castle area!
Unlock Arcade mode!
Kill over 300 zombies in Arcade mode (Without dying)
Kill over 100 zombies in Arcade mode (Without dying)
Kill over 50 ghosts in Arcade mode (Without dying)
Kill over 75 bats in Arcade mode (Without dying)
Kill over 150 ninjas in Arcade mode (Without dying)
Kill over 100 insects (Without dying)
Save Ana!