Here is the full list of all 49 Nights of Azure achievements.
Viewed an ending.
Defeated Ludegert.
Maxed out a Servan's level.
Cleared half of Arena tasks.
Defeated Corrine.
Executed trades in half of the world.
Gave 1000 orders to Servans.
Defeated Blueblood Dragon Mavelus.
Transformed into Armor form.
Collected 50% of items.
Defeated Blueblood Maiden Milaya.
Transformed into Phantom form.
Collected 50% of Servans.
Achieved 500-Chain.
Defeated Blueblood Count Rosier.
Transformed into Rabbit form.
Summoned a Servan 100 times.
Executed a trade for the first time.
Defeated 1,000 enemies.
Defeated Blueblood Cavalry Carousel.
Achieved 300-Chain.
Gave 100 orders to Servans.
Cleared first Arena task.
Completed first task.
Defeated Blueblood Dragon.
Transformed into Demon form.
Actualized a Servan for the first time.
Achieved 100-Chain.
Defeated 100 enemies.
Gave an order to a Servan for the first time.
Summoned a Servan for the first time.
Collected all achievements.
Defeated Mistral.
Defeated Christophorus.
Viewed an extra ending.
Summoned Servans 1000 times.
Actualized 40 Servans.
Actualized 80 Servans.
Executed trades all over the world.
Completed 100 tasks.
Completed 300 tasks.
Cleared all Arena tasks.
Collected all Servans.
Collected all items.
Defeated 10,000 enemies.
Transformed into Nightmare form.
Arnice equipped Hamelin's Pipe and cleared a battle.
Arnice equipped Glass Blade and cleared a battle.
Arnice achieved her max level.