Here is the full list of all 33 Boo Bunny Plague achievements.
Defeated all Four Horsemen of the Apocalypse
Defeated Death
Defeated Famine
Defeated War
Defeated Pestilence
Collected the Electric guitar.
Defeated Tyr
Collected the Frankenstrat.
Defeated Hel
Collected the Ice guitar.
Defeated Garmr
Triggered Faye's transformation
Defeated Thor
Used Gunny to defeat an enemy.
Collected the "Useless" Acoustic
Defeated TRex
Collected All Audio Lore in one game.
Hit the giant donut!
Collected the Fire guitar.
Collected the Streetz guitar.
Defeated Heimdall
has defeated Thor, Garmr, Hel ,Tyr and Heimdall
Defeated the Secretary
Defeated the Chairman
Somehow managed to fall through the world and hit a kill zone
Bounced on vikings 50 times
Stun Thor 10 times with his own hammer.
Burn enemies 50 times.
Unlocked Impossible mode!
Destroyed all of the Bunny's in the factory
You collected all of the coins in the credits
Watched the entire after credits scene
Beat the game on Impossible mode!