Here is the full list of all 35 Age of Civilizations II achievements.
Form Russian Empire
Form Australia-Hungary
Form Ottoman Empire
Form Austrian Empire
Form Japan
Form Italy
Create 50 unions
Create 25 unions
Join 50 alliances
Create 10 unions
Join 25 alliances
Create 5 unions
Join 10 alliances
Create 50 vassals
Create 20 vassals
Create 5 vassals
Create a vassal
Adopt the Monarchy government
Adopt the ideology of the City State
Adopt the Horde ideology
Adopt Republic ideology
Adopt Fascism ideology
Adopt the ideology of Communism
Adopt the ideology of democracy
Capture 1500 provinces
Join 5 alliances
Capture 750 provinces
Capture 500 provinces
Capture 300 provinces
Capture 150 provinces
Create union
Capture 75 provinces
Capture 30 provinces
Join alliance
Capture 10 provinces