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