Here is the full list of all 53 The Legend of Heroes: Trails of Cold Steel III achievements.
Completed the final chapter.
Completely filled the books section in the notebook.
Acquired over a million mira.
Completed all quests, both at the branch campus and during field exercises.
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 Juna.
Forged a strong bond with Altina.
Forged a strong bond with Musse.
Forged a strong bond with Sara.
Forged a strong bond with Towa.
Forged a strong bond with Jusis.
Forged a strong bond with Alisa.
Forged a strong bond with Elise & Alfin.
Forged a strong bond with Emma.
Forged a strong bond with Gaius.
Forged a strong bond with Millium.
Forged a strong bond with Laura.
Forged a strong bond with Fie.
Forged a strong bond with Ash.
Forged a strong bond with Kurt.
Forged a strong bond with Elliot.
Forged a strong bond with Machias.
Took all landscape photos and reported them to Vivi.
Used 100 S-Crafts in battle.
Used over 500 follow-up attacks in battle.
Raised a master quartz to level 7.
Completed Chapter 3.
Inflicted Break over 800 times.
Used Rush in battle 100 times.
Used Burst in battle 50 times.
Completed Chapter 2.
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.
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.
Completely filled the character section in the notebook.
Completely filled the cards section in the notebook.
Completely filled the recipe section in the notebook.
Completely filled the fish section in the notebook. (All 25 types of fish + Rod Lv. Max)
Gathered all 28 varieties of master quartz.
Won 600 battles.
Initiated 300 advantage encounters (including double and triple advantage).
Raised any two characters to Link Level 5.
Used Brave Order in battle over 100 times.