Here is the full list of all 53 The Legend of Heroes: Trails of Cold Steel III achievements.
Mastered Trails of Cold Steel III and earned every achievement.
Completed the game on nightmare difficulty.
Completed the final chapter.
Raised any two characters to Link Level 5.
Completely filled the battle section in the notebook.
Opened every treasure chest.
Completely filled the character section in the notebook.
Won 600 battles.
Completely filled the books section in the notebook.
Acquired over a million mira.
Initiated 300 advantage encounters (including double and triple advantage).
Completed all quests, both at the branch campus and during field exercises.
Achieved an academy grade of Prestigious.
Achieved instructor rank S.
Gathered all 28 varieties of master quartz.
Completely filled the recipe section in the notebook.
Completed Chapter 4.
Collected all radio material and reported it to Munk.
Forged a strong bond with Millium.
Forged a strong bond with Sara.
Forged a strong bond with Jusis.
Forged a strong bond with Fie.
Forged a strong bond with Towa.
Forged a strong bond with Gaius.
Forged a strong bond with Machias.
Forged a strong bond with Laura.
Forged a strong bond with Elise & Alfin.
Forged a strong bond with Alisa.
Forged a strong bond with Elliot.
Forged a strong bond with Emma.
Forged a strong bond with Kurt.
Forged a strong bond with Ash.
Forged a strong bond with Musse.
Completely filled the fish section in the notebook. (All 25 types of fish + Rod Lv. Max)
Forged a strong bond with Juna.
Forged a strong bond with Altina.
Took all landscape photos and reported them to Vivi.
Used Burst in battle 50 times.
Completely filled the cards section in the notebook.
Used Rush in battle 100 times.
Completed Chapter 3.
Raised a master quartz to level 7.
Inflicted Break over 800 times.
Used 100 S-Crafts in battle.
Completed Chapter 2.
Used over 500 follow-up attacks in battle.
Won a battle with a tactical bonus of x3.0 or greater.
Used Brave Order in battle over 100 times.
Earned an S-Rank on any chapter.
Completed Chapter 1.
Won 100 battles.
Completed the orienteering exercise.
Completed the prologue.