Here is the full list of all 12 GundeadliGne achievements.
Finish the game in Duet Play with both players alive.
Clear 25 lines in Eternal Babel mode.
Defeat every opponent in Demonic Challenge mode.
Finish the game on Demonic difficulty.
Finish the game with every character.
Get 6 Alter Breaks in one game.
Finish the game on Advanced difficulty.
Finish the game on Standard difficulty.
Defeat the true last boss.
Finish the game on Novice difficulty.
Finish the game without continuing.
Keep the holiday spirit alive.