Full list of all 20 Open World Game: the Open World Game achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Read every Journal Entry.
100% Completion + 1%.
Reforge every Legendary Weapon.
Collect everything.
Complete every Side Quest.
Catch every Fish.
Catch every Herptile.
Conquer every Fortress.
Collect every Mask.
View every Lookout Point.
Collect every Feather.
Say the perfect words in every Relationship.
Reach Lv 100.
Visit every Fast Travel location.
Finish the Completionist Skill Tree.
Unlock every Skill.
Light every beacon.
Finish the Generalist Skill Tree.
Finish the Main Quest.
Finish the Speed-Runner Skill Tree.