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