Here is the full list of all 50 The Walking Dead Onslaught achievements.
Earn All Achievements
Fully Upgrade All Weapons in the Armory
Kill A Walker With Every Weapon in the Game
Replay and Finish Any Chapter from Chapter Select
Complete all Requisitions
Complete all of Sydney's Requisitions and Fully Upgrade the Windmill
Complete all of Julia's Requisitions and Fully Upgrade the Forge
Complete all of Hazel's Requisitions and Fully Upgrade the Stockpile
Complete all of Oliver's Requisitions and Fully Upgrade the Clinic
Fully Upgrade all Buildings in Alexandria
Complete Alexandria (Max Population, Buildings Fully Upgraded, Campaign Complete)
Finish Chapter 7: The Promise (Any Difficulty)
Finish Chapter 7: The Promise (Veteran)
Finish all Campaign Chapters (Veteran)
Discover all Weapons for the Armory
Complete All Scavenger Sites
Reach Maximum Population (25) in Alexandria
Unlock all Scavenger Sites
Finish Chapter 6: When Dust Settles (Any Difficulty)
Finish Chapter 6: As Dust Settles (Veteran)
Construct all Buildings in Alexandria
Finish Chapter 5: Roads Less Traveled (Any Difficulty)
Finish Chapter 5: Roads Less Traveled (Veteran)
Finish all Campaign Chapters (Any Difficulty)
Kill a Spike Walker
Kill 1,193 Walkers
Complete all of Rajul's Requisitions and Fully Upgrade the Town Hall
Finish Chapter 4: Around the Bend (Any Difficulty)
Finish Chapter 4: Around the Bend (Veteran)
Kill 5 Walkers With One Explosive Trap
Finish Chapter 3: The Rabbit Hole (Any Difficulty)
Finish Chapter 3: The Rabbit Hole (Veteran)
Fully Upgrade Any Weapon in the Armory
Bring 10 New Survivors to Alexandria
In Scavenger, Get to the Rendezvous Point Without Taking Damage from the Wall
During Evac, Survive for 3 minutes after the Van Arrives
Finish Chapter 2: Strange Circumstances (Veteran)
Upgrade a Weapon in the Armory
Finish Chapter 1: Desperate Days (Veteran)
Finish Chapter 2: Strange Circumstances (Any Difficulty)
Kill an Armored Walker
Discover a New Weapon for the Armory
Complete a Scavenger Site
Find a Supply Cache in a Supply Run
Finish Chapter 1: Desperate Days (Any Difficulty)
Choke 30 Walkers
Construct the Town Hall in Alexandria
Bring a New Survivor to Alexandria
Finish Prologue: What Comes Before and After (Any Difficulty)
Finish the Tutorial