Here is the full list of all 26 Blade Symphony achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Bow every duel for 100 duels consecutively.
Win a 2v2 game.
Use the heart emote on Valentine's Day.
Kill two people with one attack.
Duel on ffa_community.
Participate in a duel on the map District.
Duel on duel_monastery.
Duel on duel_temple.
Be on the winning team for a round of Capture Point.
Capture the a control point for your team alone.
Be on the losing team for a round of capture point
Draw a round of capture point.
Win a round of Hero mode as the hero.
Win a 1v2 duel.
Win a 2v1 duel.
Participate in a duel on the map Winter.
Win a duel as each character.
Kill a target while they bow.
Use an emote just before killing an opponent.
Win your first duel.
Finish a round with full health without bowing.
Win a duel after sitting during the duel.
While others battle free-for-all, you show victory in a duel.
Kill someone with a grab.
Cancel a grab with your grab.
Complete the in-game tutorial.