you're better off using Resolve than Odin because the boss hits for a whopping 55k
for the stage, kill the non red enemies first because the red ones deal the least damage and have the most hp (non red enemies have a pitiful <1500 HP)
during midbosses kill one asap (green > blue > red, since green attacks every turn while red you get 3 turns) with abilities (lucifer, rippers. gravities, whatever you have) and then whittle down the other
boss is pretty trivial