Here is the full list of all 28 Headbangers: Rhythm Royale achievements.
Grab 20 Item Boxes
Grab an Item Box
Complete Challenge card #1
Complete Challenge card #2
Complete Challenge card #3
Complete Challenge card #4
Complete Challenge card #5
Complete Challenge card #6
Complete Challenge card #7
Complete Challenge card #8
Complete Challenge card #9
Win a tournament
Win 10 tournaments
Win 20 tournaments
Win 50 tournaments
Wear 20 different garments in-game
Get first place in a Bonus Round
Participate in 100 tournaments
Participate in 10 tournaments
Participate in 25 tournaments
Participate in 50 tournaments
Participate in 75 tournaments
Spend 10 000 Crumbs
Spend 50 000 Crumbs
Spend 100 000 Crumbs
Spend 180 000 Crumbs
Complete Challenge card #10
Complete Challenge card #11