-Unlock the following alternate endings by performing the corresponding tasks:

ENDING - HOW TO UNLOCK
Dark Assembly - Force proposals in the Dark Assembly fifty times.
Etna Heroine - Get at least 100 ally kills before Chapter 5, Stage 4, then kill Maderas when prompted.
Flonne Tragedy - Get at least 50 ally kills before Chapter 3, Stage 4, then kill Hoggmeiser when prompted.
Good/Best - Beat the game without any ally kills.
Item God - Kill an Item God or Item God 2.
Midboss - Lose to the mid-Boss of Chapter 1, 4, 6, or 10.
Normal - Have at least one ally kill and do not fulfill the requirements for any other ending.
Overthrowing Earth - Pass the "Human World" proposal at the Dark Assembly, then complete the Human World stages.

-Unlock the following alternate endings in Etna mode by performing the corresponding tasks:

ENDING - HOW TO UNLOCK
Beauty Tyrant Overlord Etna - Pass the proposal for Alternate Netherworld and The Mysterious Seal in the Dark Assembly, then defeat Priere, Marjoly, and Baal.
Normal - Beat the last chapter in Etna mode.