Here is the full list of all 14 Kingdom Wars 4: The Plague achievements.
Successfully lay siege in combat in campaign mode
Destroy enemy army in a field combat in campaign mode
Fully complete tutorial campaign
Start the game in regular online mode
Defeat enemy in a naval battle
Successful defend your town in campaign mode until enemy army retreats
Conquer Constantinople the Byzantine Empire in Campaign Mode
Conquer New Sarai from the Golden Horde in Campaign Mode
Conquer Cairo from the Mamluk Sultanate in Campaign Mode
Conquer Algier from the Zayyanid Dynasty in Campaign Mode
Conquer Rome from Papacy in Campaign Mode
Conquer Moscow from the Duchy of Moscovy in Campaign Mode
Conquer Stockholm from the Kingdom of Sweden in Campaign Mode
Conquer Athens from the Kingdom of Aragon in Campaign Mode