Here is the full list of all 28 EMPTY SHELL: DEMO achievements.
Find 5 secret rooms
Kill 10 Spitting Spiders
Kill 350 enemies with the Old Axe
Kill 350 Small Spiders
Death count: 10
Collect all the documents in the Prologue
Kill her with her own weapon
Kill 400 Walking Soulless
Use a Device
Kill the Hand in less than 20 seconds on NIGHTMARE difficulty
Find 5 documents
Rounds fired: 200
Deploy a Gadget
Upgrades Cost: >1000
Kills count: 50
As big as an elephant
Rounds fired: 100
Kills count: 15
Death count: 1
Complete the Demo
Complete the Demo on Nightmare difficulty
Complete the Demo on Hard difficulty or higher
Complete the Demo on Medium difficulty or higher
Complete the Demo on Easy difficulty or higher
Finish a level with only melee weapons
Survive the whole Prologue on NIGHTMARE difficulty with the same volunteer
Leaving Building C
Finish a level without taking any damaged on NIGHTMARE difficulty