Here is the full list of all 11 A Modest Legacy achievements.
Win a game against 1 or more kingdoms
Win a game against 9 kingdoms
Research all topics in a single game
Max out all materials in a single game
Take out 100 enemies
Destroy a building using artillery
Destroy a boat using a ballista
Build 500 buildings
Place a ballista in a tower for some extra defense
Ally 2 kingdoms at once
Create 20 outposts