The Breakdown Add-on for State of Decay has 8 achievements worth 100 gamerscore.
Unlock All Heroes.
Reach Breakdown Level 6.
Execute 50 Stealth Kills (Breakdown Level 5 or Higher).
Destroy 5 Juggernauts (Breakdown Level 5 or Higher).
Collect 150 Resources (Breakdown Level 4 or Higher).
Perform 50 Zombie Executions (Breakdown Level 3 or Higher).
Go Out in a Blaze of Glory (Breakdown Level 1 or Higher).
Kill 5 Bloaters (Breakdown Level 2 or Higher).