Here is the full list of all 25 Army General achievements.
Loose 10 units of Type VII C u-boats in combat
Loose 20 naval units by the combat even "scuttled"
4 objects
By a unit in the HQ
Change 1 Officer in a unit
Load an external map
Upgrade a regiment to a divison
Defeat 50 enemy units by forcing them to surrender
Capture 25 ports from the enemy
Win the Mare Nostrum campaign
Win the British Operation Compass campaign
Kill 1000 infantry units
Kill 100 fighter units
Destroy 5000 strength points of tank units
Buy 50 tank units
Add support unit "Flame tank Platoon" to a German tank unit
Add 150 support units to formations
Shatter 75 units
Kill 5 units of Matilda II tanks
Exchange 30 officers of tank units
Sink 25 ships with submarines
Destroy 250 units with bomber units
Kill 100 units with fighter units
Win all tutorial maps
Win all campaigns and single maps of the base game