Here is the full list of all 24 Company of Heroes 3 achievements.
Purchase a Detachment
Decide where to go after Salerno
Complete a Mission or Skirmish without reinforcing a Squad
Complete Calabria
Complete a Mission or Skirmish without losing a Squad
Complete Mission Zero
Issue an order in Tactical Pause
Gain 100% loyalty with Valenti
Gain 100% loyalty with Buckram
Gain 100% loyalty with Norton
Collect all Soldier Stories
Break the Volturno Line
Break the Gustav Line
Uncover a conspiracy
Silence Anzio Annie
Save Monte Cassino
Heal a unit with ice cream
Complete the Italy Campaign
Complete the North Africa Operation
Issue 500 orders in Tactical Pause
Win a Multiplayer or Skirmish match
Win 25 Multiplayer or Skirmish matches
Use Battlegroup Abilities 100 times
Win a Multiplayer or Skirmish match without losing a Victory Point ticket