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