Here is the full list of all 32 Bunny Must Die Chelsea and the 7 Devils achievements.
Defeat the Crimson King, Pope Cucurbita, without stopping time.
Get abducted by a UFO.
Defeat the Reaper, Selene Millfall, using the Faust Samurai.
Defeat the Moon Shadow, Endymion, using the Sylph Shooter.
Clear Bunny Must Die mode.
Clear Bunny Must Die mode in under 2 hours.
Clear Bunny Must Die mode in under 1 hour.
Clear Bunny Must Die mode with 100% items obtained.
Clear Bunny Must Die mode in under 2 hours with 100% items obtained.
Clear Bunny Must Die mode with less than 15% items obtained.
Clear Chelsea and the 7 Devils mode.
Clear Chelsea and the 7 Devils mode in under 2 hours.
Clear Chelsea and the 7 Devils mode in under 1 hour.
Clear Chelsea and the 7 Devils mode with 100% items obtained.
Clear Chelsea and the 7 Devils mode in under 2 hours with 100% items obtained.
Clear Chelsea and the 7 Devils mode with less than 15% items obtained.
Die 1,000 times.
Collect 100,000 Time Gems.
Block 1,000 times.
Defeat the First Devil, El Bobonboi, in her Crazed Insane Mode.
Defeat the Second Devil, Pure Aahaah, using the Faust Samurai.
Defeat the Third Devil, Nuko do Maron, within 30 seconds.
Defeat the Fourth Devil, Baron Bramdeau, within 30 seconds.
Defeat the Fifth Devil, "Eye of the 13th Sage," without taking any damage.
Defeat the Pumpkin King, Lord Pumpkish, without taking any damage.
Defeat the Jester King, Choker Joker, using the Spike Hammer.
Defeat the Sixth Devil, Halloween Alice, without taking any damage.
Defeat the Final Devil, Subaru Septentrion, without using any Elixirs.
Defeat the Fairy Princess, Chelsea Mamanaju, without using any Bunny Dolls.
Defeat the Time Rabbit, Bunny the Honey White, without using any Elixirs.
Survive against the God of Calamity, Nomos Dechronus, in his Rage Mode for 20 seconds.
Obtain all other achievements.