Instructions
Ares&' First Form
Start the game and play through the "God of War 2" levels until you reach the Temple of the Oracle. While you are playing, level up both the "Rage of the Gods" and "Army of Hades" spells. These two spells will be important later.
Play the Temple of the Oracle level, which is the final level. Save whenever possible, and keep yourself at full strength by using all of the health and mana chests. You know you&'re approaching the final battle when a cutscene video plays introducing Kratos to Ares.
Cast "Rage of the Gods" once battle begins. This makes Kratos move faster and hit more powerfully.
Cast "Army of Hades" to summon an army of soldiers who will attack Ares.
Block Ares&' attacks. Your attacks won&'t cause a lot of damage, so focus more on defending yourself while letting the "Army of Hades" spell do most of the work. Attack when possible, but be prepared to defend yourself.
Continue casting "Army of Hades," blocking and attacking Ares until a "circle" icon appears on Ares&' head. Press the buttons that appear on the screen to defeat Ares&' first form.
Ares&' Second Form
Use "Rage of the Gods" after Ares reveals his second form. He will also produce your family, who you will need to protect from Kratos clones.
Use "Army of Hades" and "Plume of Prometheus" to damage groups of enemies attacking your family. You should try to attack multiple, or all, enemies at once instead of focusing on a single enemy at a time.
Use "Rage of the Gods" when the Kratos clones armed with Blades of Artemis appear. Use the "Army of Hades" again to damage them. Continue attacking until the clones are defeated and Ares&' third form returns.
Ares&' Third Form
Block his attacks when possible. All but two of his attacks can be blocked--the others should be dodged. Note also that you share a health bar with him now. When you damage him, you heal yourself--unfortunately, the converse is also true.
Watch for him raising his hand, as this means he&'s going to launch a large fireball at you. This you&'ll have to avoid, as you can&'t block it.
Look out for when he ducks below the water, as it means he&'ll pop up and shoot four columns after you.
Attack him when he stops to growl or roar at you. Use your best fighting combos to attack him until you are prompted to press the "Circle" button to initiate a sort of "tug of war" with tapping repeatedly.
Repeat the process of attacking, blocking and dodging until you defeat Ares.