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