This achievement is obtained for finishing the game. Hurray!
The last level returns you to the BLS-4 Research Ward to acquire the last ability upgrade which allows the Carrion to turn into a human form.
Once human, you need to pass through a series of hand scanning stations and eventually leave the facility to live your best life as a hard working business professional.
What new challenges await it? With no noticeable labor skills and an insatiable apatite, times will be hard for Carrion in its young life. Perhaps it will adapt quickly to the fast pace modern lifestyle the city holds. Maybe it will participate in streaming food-eating challenges and make income from charitable viewers. Maybe, just maybe, one day, it will learn to love.