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