Here is the full list of all 33 OCTOPATH TRAVELER II achievements.
Rode the ferry to a new land.
Learned a skill for the first time.
Embarked on a journey.
Acted at maximum boost for the first time.
Broke an enemy for the first time in battle.
Unlocked all achievements.
Gathered all eight travelers.
Completed Osvald's story.
Completed Castti's story.
Completed Throné's story.
Completed Ochette's story.
Completed Partitio's story.
Completed Agnea's story.
Completed Temenos's story.
Completed Hikari's story.
Learned a job's divine skill.
Completed Agnea and Hikari's Crossed Path.
Completed Temenos and Throné's Crossed Path.
Completed Castti and Ochette's Crossed Path.
Completed Osvald and Partitio's Crossed Path.
Returned dawn to the world.
Approached the end of your journey.
Learned all EX skills.
Learned all secondary jobs.
Traveled to every location on the map.
Dealt 9,999 or more damage.
Defeated the netherworldly threat.
Finished all side stories.
Obtained all records.
Obtained all battle-tested equipment.
Gleaned information from 100 townspeople.
Brought along four townspeople at once.
Soothed or knocked 100 townspeople unconscious.