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