A simple guide on how to beat Dianne and get all the endings in Demon King Domination: Deluxe Edition.
When the fight begins, use “charge” until you are defeated.
Use the battle guide to reach phase 5, then use “charge” until you are defeated.
Use the battle guide to win phase 5.
Ending 3 (hard mode version):
After getting ending 3, start a new game and enter Hard Mode. Use the battle guide to win phase 5.
Heal, charge, counter.
Counter, charge, heal, attack, counter, charge, attack.
Charge, attack, counter.
Repeat until you win.