Here is the full list of all 16 FRAGROOM: Defenders achievements.
Install and launch the game
Win the game
Freeze the bus at least once
Set 5 zombies on fire with a single shot
Freeze 5 zombies with a single shot
Win the game using only the default weapon
Use the heavy Machine gun in every round and win the game
Shoot 10 barrels during the game
Score maximum points in a game
Used all available weapons in a round
Score 10 headshots in a run
Win the game without damage to Main Base
Kill all flying zombies before they land on the Main Base
Get all the achievements
Lose all rounds in the game
Win the round with Main Base HP under 20%