Here is the full list of all 26 Don't open the doors! achievements.
Explode the main door.
Upgrade diamond armor to max.
Kill 5 enemies with a single hammer srike.
Die 25 times.
Squash 100 chests.
Collect bee glue.
Don't take any reward from Mr. Bee and pass through the hive gates.
Wear the glasses.
Squash 2000 objects.
Defeat the Great Cactus.
Carry a large amount of money.
Kill 10 enemies with a single hammer srike.
Find a book.
Bring the megabomb.
Kill 50 bees.
Kill 1000 bugs.
Defeat the Arik.
Break the beetlejuice cauldron.
Drink 200 pots of compote.
Read all the diary parts.
Beat all the doors.
Kill 1000 flies.
Find all the gold keys.
Kill 20 enemies with a single hammer srike.
Defeat the Pumpkinello.
Kill 50 spiders.