Here is the full list of all 18 Crown Champion: Legends of the Arena achievements.
Win the royal tournament.
Pass the trials.
Defeat the champion of Willowsfall.
Defeat the champion of Tonstead.
Create a garden on your estate.
Defeat the champion of Wainton.
Build stables on your estate.
Defeat the champion of Stonyford.
Defeat the champion of the Dunes.
Get married.
Upgrade your main house.
Build a bath house on your estate.
Defeat the champion of Waldley.
Defeat the champion of Sandworth.
Defeat the champion of Greenwood.
Build a guard tower on your estate.
Defeat the champion of the Temple of Ueres.
Defeat the champion of Ada's Alehouse.