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