Here is the full list of all 21 The Last Stand Legacy Collection achievements. It takes around 4-5 hours to unlock all of the achievements on Windows.
The Last Stand 2 - Five survivors
The Last Stand 2 - Reach Union City
Die during your second Last Stand
The Last Stand 2 - Use the hunting bow
The Last Stand 2 - Leave Glendale
The Last Stand 2 - It's chainsaw time again
The Last Stand 2 - First night survived
The Last Stand - Saved by the helicopter
The Last Stand - Five survivors join you
The Last Stand - Equip the Chainsaw
The Last Stand - Equip the Shotgun
The Last Stand - First survivor located
The Last Stand - First night survived
The Last Stand: Union City - Visit the first house
The Last Stand: Union City - Reach Brookvale
The Last Stand: Union City - Joined by Kelly
The Last Stand: Union City - Reach the Hospital
The Last Stand: Union City - Reach the Stadium
The Last Stand: Union City - Is it over?
Die during your Last Stand
Die during your Last Stand in Union City