Here is the full list of all 22 MidBoss achievements.
Destroy 50 inanimate objects with magic missile
Import a death card
Unlock the power of Mid OS and boot up MidBoss Classic
Start a game with 6 pieces of grave goods
Liberate 450 cratefish
Pretend to be a smithy 200 times
Share a death card on social media
Meet the cat merchant
Possess your first creature
Gain a major blessing from all four gods
Cheat death
Beat the game
Get a lucky drop with a x16 multiplier
Unlock all retro mode filters
Kill the skeleton and zombie from the intro cutscene
Master every form in the game in a single run
Accumulate 5,000 yarnballs in a single run
Kill 6 creatures with a single attack
Vandalize 50 shrines
Obtain the golden ticket
Break the rules of engagement and beat the lich lords
Go through the glitch door