Here is the full list of all 33 Ys: The Oath in Felghana achievements.
Enabled "No-Fall" mode.
Completed all other achievements.
Escorted Elena to safety on every difficulty level.
Escorted Christof to safety on every difficulty level.
Began the game on Very Easy.
Bested the master of the mountains in one-on-one combat.
Conquered Boss Rush on Nightmare.
Defeated "The Deadliest Cuteness."
Died over 10 times on a single boss.
Beat the game on Nightmare.
Beat the game on Inferno.
Conquered Boss Rush on Hard.
Killed 500 Selnades across all playthroughs.
Beat the game on Hard.
"Killed" 50 immortal beasts without using the Silver Chimes.
Sold Randolph's ring to Cynthia.
Killed 2,000 Mozgouz across all playthroughs.
Beat the game on Very Easy.
Spent over 10 hours in a single playthrough.
Conquered Boss Rush on Normal.
Beat the game on Easy.
Beat the game in under 5 hours.
Defeated the final boss without taking any damage.
Achieved max level.
Beat the game on Normal.
Maxed out all equipment.
Acquired every jewel.
Encountered every enemy in the game, excluding bosses.
Spoke with every character in the game at least once.
Saved all of Hugo's pikkards.
Completed Anya's treasure-hunt game.
"Measured" Elena.
Defeated 5 or more enemies (except Mozgouz) at the same time.