Here is the full list of all 25 Hotel Transylvania 3: Monsters Overboard achievements worth 1,000 gamerscore.
Collect all other Achievements.
Defeat the Fiendish Flower and retrieve the first part of Neptune's Compass.
Defeat the Cruel Crustacean and retrieve the second part of Neptune's Compass.
Defeat the Dastardly Dragon and retrieve the final part of Neptune's Compass.
Collect your first treasure.
Collect half of the Treasures hidden in the Lost Islands.
Collected every single Treasure hidden in the Lost Islands.
Defeat 5 enemies in a single night.
Have 5 of each Impa type at once for more than 5 seconds.
Collect 5 Imparite Stones in a single night.
Defeat a Coconut Crab while it's stunned.
Retrieve an object from a clam without it closing on anyone.
Unlock the third Impa Portal.
Unlock half of all Impa Portals.
Unlock every single Impa Portal.
Have 30 Vampimpa at once for more than 5 seconds.
Defeat any enemy other than a Feeble Flower with nothing but a single Wolfimpa.
Defeat an enemy with the impact from a thrown Frankenimpa.
Use Mummimpa's Magic Sand to block the smell trail from a Stinkbulb.
Collect 3 objects from Giant Clams.
Hit an enemy with a ricocheted Mummimpa.
Complete the tutorial and meet up with Ericka, Johnny and Dennis.