TEMPLE OF HADES - DAMAGE CAP (4.2 Bi) - ARIES SHION - ARTEMIS & CLASSIC APHRODITE

If you have:
Sufficient Defense Pierce (over 1300, ideally). Equip the Cosmo mixer, Cosmo with an inscription.
The Heavens and Earth Cosmo to boost Defense Pierce.
With all these in place, you should be able to "break" the boss's defense.
Tips for Shion:
He always targets the saint with the lowest HP, like Poseidon's summon.
You also need a speed above 600 to outspeed Shion; you might consider using the Cosmo Decelerator for this.