You really need to use Counter Fighting style (the blue one), its the most overpowered style in the game, with good build you dont even need to dodge until around new game +5.

The only thing you really need is a "Crimson Counter", which is a Counter with a flower shard from the boss "The Deer God".
The rest of the build is at your disposal (it's best to go dmg to kill him faster).

Dunno what I can say for the first two phases than just "dodge everything and deal dmg to the boss", everyone has own playstyle so do your best!

Be sure that u have fully charged Counter bar before Phase 3, then just wait until his air sucking and spam Counter, with enough luck you will counter every dmg he can deal and beat him taking 0 damage.

Good Luck.