Here is the full list of all 13 Die by the Blade achievements.
Kill an opponent in an online duel or tournament
Execute any finisher
Assign any customization item to your character
Customize any weapon
Win an offline duel or tournament against AI
Die in any duel or tournament
Start an offline duel or tournament
Execute any three-part combo with any weapon
Win an online duel or tournament without receiving damage
Finish an online duel or tournament
Win 5 online duels or tournaments without receiving damage
Host an online duel or tournament
Kill 20 opponents in online duels or tournaments