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