Here is the full list of all 17 Metal Tales: Fury of the Guitar Gods achievements.
Beat Hrungnir
Beat Cyborg
Beat Heikegami
Beat Cernunnos
Beat Kresnik
Beat Ottavio
Beat Timo
Beat Kuk
Beat level 1: Horns & Skulls
Beat level 2: Fall of the Hammer
Beat level 3: Nightmare Fest Camp Zone
Beat level 4: Nightmare Fest Main Sta
Beat level 5
Beat challenge room no damage
Spend 100 coins in the shop
Save 5000 minions
Die 100 times