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