Here is the full list of all 21 Fallen: A2P Protocol achievements.
Kill everyone using only flametrhower in one mission
Fully Equip all your caravaneers in one mission
Kill 4 enemies with one hit
Kill everyone using only rocks and grenades in one mission
Kill everyone using only shotguns in one mission
Kill everyone using only rifles and smgs in one mission
End a mission without taking any hit
Kill everyone using only snipers in one mission
Recruit more than 3 caravaneers
Kill everyone using only pistols in one mission
Kill everyone using only rocket launchers in one mission
Level up all skills in Vitality Branch
Level up all skills in Strength Branch
Perform a healing more than 5 times in a single mission
Recharge your caravan's A2P
Complete a mission without losing any caravaneer
Kill everyone using only melee weapons in one mission
Kill 10 enemies using overwatch skill
Scavenge all the available items within a mission
Level up all skills in Perception Branch
Level up all skills in Agility Branch