Here is the full list of all 20 The Colony achievements.
Take out a Pod
Take out an Egger
Take out a Hanger
Take out a Crawler
Complete your mission aboard the Leah Colony
Destroy all security blast doors on the station
Take out a Chanter
Take out a Cultist
Take out a Gunner
Take out a Hunter
Take out a Leeched One
Take out a Leviathan
Take out a Marine
Destroy your deceiving AI companion
Complete the game without dying
Destroy the queen
Destroy Dr. Raynor in his first form
Finish off Dr. Raynor..
Take out a Slimemaid
Disable a defense turret