Here is the full list of all 21 Ys SEVEN achievements.
Complete the game on Nightmare difficulty.
Obtain all other achievements.
Complete the game on any difficulty.
Raise all of any one character's skills to max level.
Learn every skill.
Unlock all bestiary entries for all non-boss, non-titano foes.
Synthesize all Dragon Stone weapons.
Conquer the Moon Dragon, Ze-Kalion.
Synthesize each Spirit Elixir at least once.
Buy every item from the Zanzibar Firm.
Conquer the Sea Dragon, O-Balon.
Conquer the Wind Dragon, Mu-Anti.
Conquer the Earth Dragon, Rada-Manj.
Defeat all titanos.
Find all the missing pikkards.
Conquer the Flame Dragon, Angue-Barl.
Survive against a beast intended specifically to kill you.
Die by walking over thorns.
Defeat Geis in one-on-one combat.
Escort Tia back to Altago City completely unscathed, and without using any healing items.
Die by drowning.