Here is the full list of all 20 Viola achievements.
Viola retains the connection to Vylna, forging her own path.
Reach Support Level S with Sybil.
Complete every Personal Quest.
Reach Support Level S with Emerald.
Reach Support Level S with Arti.
Reach Support Level S with Justice.
Reach Support Level S with Ceryn.
Viola returns home, destroying the world of Vylna.
Viola remains in Vylna, never returning home.
Recruit all 10 characters.
Reach Support Level S with Soleil.
Reach Support Level S with Mallow.
Reach Support Level S with Niko.
Reach Support Level S with Momo.
Reach Support Level S with Fenrys.
Learn all nine songs.
Buy something in the Catshop.
Recruit a full party.
Learn Viola's first song.
Beat the first level.