Here is the full list of all 35 The Last Stand: Aftermath achievements.
Kill a Volunteer
Reach The Mountains
Open the gates at the HERC checkpoint
Discover the modified HERC device
Acquire a mutation
Craft an item at a crafting station
Interact with a Supply Cache
Complete the tutorial
Reach The Sunken City
Reach Hell
Survive in No Man's Land
Reach Level 10
Reach Level 50
Reach Level 100
Died 10 times
Trigger a trap, with fatal consequences
Spend Knowledge points to max out a skill upgrade
Kill a Charger
Kill a Spitter
Kill a Leaper
Kill a Burster
Kill a Flamer
Kill an Armored Charger
Kill 1000 Infected
Survive a Horde
Collect 100 Knowledge
Activate the radio tower
Lower the bridge in Leighton City
Complete the main quest line
Complete 5 Runs
Craft 25 items at a crafting stations
Craft an improvised weapon
Purchase an item from the travelling merchant
Collect 25 Supply Bags
Use Antiviral 25 times