The warrior marked in red was prophesied to be the end of the gods. That warrior, in the estimation of the gods, was Kratos' brother. So the gods killed him.
They were wrong.
Kratos tattooed himself in red with a replica of his brother's birthmark.
Ares realized this meant Kratos was the ultimate warrior and began using Kratos as a pawn in his games with the other gods. Kratos got trapped in the crossfire.
As Ares' favored toy, Kratos was a ridiculously successful Spartan warrior, and through his victories eventually got lead into Ares' trap.
He found his army overwhelmed by barbarian hordes and on the brink of defeat, so he was forced to call upon Ares for help and swear allegiance to him in order to survive.
Now he was a servant of Ares' will.
Wanting Kratos to be unfettered by mortal attachments so that his servant could focus on being the perfect warrior, Ares tricked Kratos into slaughtering his own family.
Enraged, Kratos rebelled against Ares and was cursed to have the ashes of his family fused to his skin in return.
Ares unleashes the furies upon Kratos as punishment, and they torment him until he can finally kill them.
Finally he is freed of service to Ares when he kills the guy who maintains his oath to Ares. Kratos didn't want to kill any more innocents, but the guy pleaded to die...so finally Kratos was free.
Kratos then saved Helios from Morpheus, saving Greece. During the quest to save the sun he is plagued by visions of his daughter. Persephone promises Kratos that she can reunite him with his daughter in exchange for all his power. He takes the deal, only to discover she was responsible for Helios being imprisoned as part of her plot to destroy the gods and mankind. She taunted Kratos with the fact that he would only briefly be with his daughter before she would die again, due to her plan.
Kratos was forced to leave his daughter once more and regain his powers to save the world.
Ares began waging war on Athens because he was jealous of Athena. Because gods were forbidden to fight each other, Athena asks Kratos to be her champion, and offers him revenge against Ares, and offers him forgiveness for the things that haunt him.
He is tasked with retrieving Pandora's Box.
He is force to battle his way through the legions of Ares' monsters rampaging through Athens, efore being instructed to journey through the Desert Of Lost Souls to find the titan, Cronus. Had to climb his way onto Cronus and enter the Pandora's Temple upon his back to retrieve Pandora's Box.
Ares kills Kratos and steals the box from him.
Kratos fights his way out of the underworld and back to life.
Finally, Kratos reclaims the box and opens it, using its power to grow to Ares' size and fight him.
As Kratos battles Ares, Ares forces Kratos to try and save phantom versions of his family...from phantoms of himself, only to watch them die again. Kratos breaks free of the illusion and finally slays Ares.
Kratos is granted forgiveness for the things he did, only to realize that the forgiveness he was promised did nothing to dispel the guilt and nightmares that haunted him.
Vengeance achieved and all hope lost to him, Kratos tries to commit suicide. Instead, Athena saves him and makes him the new God Of War.
As the God Of War, Kratos is given visions of his long-thought-dead mother still living and imprisoned in Atlantis. He frees her only to be told that his true father is Zeus. Before she can explain the situation, the gods turn her into a monster, and he is forced to kill his mother. Kratos then rescues his brother from the realm of Thanatos(death), only for Thanatos to kill him. Kratos slays Thanatos in return, and then buries his brother.
At this point Kratos is just overloaded with rage and vengeance, and he unleashes his Spartan armies on Rhodes, and personally joins them as a giant rampaging god. An eagle robs him of part of his godly power, including his size, and animates the Colossus Of Rhodes to kill him.
Finally, Zeus offers Kratos the Blade Of Olympus to kill the Colossus, telling Kratos to infuse his godly power into the blade. He kills the Colossus only to be trapped and crushed under its debris. The eagle arrives revealing itself to be Zeus. Zeus takes the Blade and uses it to kill Kratos when Kratos refuses to be his servant.
Kratos is dragged down into the Underworld where he is saved by the titan Gaia, who gives him the strength to escape death once more.
He escapes, and embarks on his quest to find the Fates and regain his godhood so he can get his revenge.
In the process he frees Prometheus of his eternal torment.
Kratos accidentally kills one of his Spartan soldiers, only to learn from the dying man that he was the last Spartan, as Zeus had destroyed Sparta....obviously enraging Kratos MORE.
He then killed the Fates and took control of his own destiny, traveling back in time, he took the Blade Of Olympus from the hands of Zeus who had just finished killing the past Kratos.
Kratos almost kills Zeus only to have Athena interfere. As Zeus attempts to flee, Kratos tries to kill him once more, but Athena throws herself in the way and is killed instead. Dying, she explains that Zeus is his father, and Zeus is trying to save himself by breaking the patricidal cycle of the kings of the Greek gods. That Zeus didn't care about Greece, only himself and his position as king of the gods. Kratos, obviously, just derives more rage and despair from this - Athena having been his only friend and, as it turns out, his sister.
The dying Athena pleads with him to stop his revenge, but Kratos vows to slay all the gods.
He travels back in time to the Titanomachy and bring the Titans into the present to lay siege to Olympus.
As the Titans lay siege Kratos and the Titans begin killing gods, and gods begin killing Titans. Reaching Zeus, Gaia and Kratos are blasted down the mountain by lightning. Gaia then reveals that the Titans aren't on Kratos' side. They too had been using him as a pawn.
Kratos tumbles down the mountain into its very depths and find himself once again in the Underworld, where most of his godly might is drained away by the River Styx.
There he meets the spirit of Athena, who once again offers to help him. Suspicious of her sudden change of heart, but in need of help, he accepts.
He sets out to extinguish the flame of Olympus. Along the way he kills a bunch of gods and messes up some Titans. Eventually he rescues Pandora, an artificial little girl that he learns was created as a key to Pandora's Box, and became a prisoner of Zeus' after he became paranoid of Kratos reaching the box again. Kratos becomes fond of Pandora, because she reminds him of his daughter.
When they finally reach the flame of Olympus, Kratos tries to stop Pandora from sacrificing herself to unlock Pandora's Box, but as he battles with Zeus she does it anyways.
Kratos discovers the Box was empty, and Zeus taunts him for failing and Pandora sacrificing herself for nothing.
As they battle, Zeus and Kratos are attacked by Gaia. They battle Gaia and Kratos steals her power to restore his own. He then simultaneously kills Zeus and Gaia. He is then attacked by Zeus' enraged spirit, which traps Kratos within his own mind, his nightmare world of fear and guilt and despair. Trapped in his mind, Pandora's spirit reaches out to him and allows Hope to surface within him.
Kratos uses hope to free himself from his mind and return to the real world, forces Zeus' spirit back into his body thereby bringing him back to life long enough for Kratos to beat the eternal crap out of Zeus once and for all.
Athena's ghost arrives and congratulates Kratos, asking him to surrender the power of Pandora's Box. Kratos tells her it was empty and is struck with remorse and guilt that Pandora's sacrifice was for nothing. Athena doesn't believe Kratos, saying she had stored the most powerful weapon, Hope, in Pandora's Box to counteract all of the evils.
She demands he return the power of to her so that she can rebuild the world and rule it.
Athena then realizes that when Kratos opened the Box the first time to, to kill Ares, he had become infused with the power of Hope and it had been hidden within his guilt, despair, and rage for all those years since, only releasing it when he finally learned to forgive himself with Pandora's help.
And she realized that opening the box back then had also unleashed all the evils, and that they had infected the gods themselves. The gods had been corrupted and became more and more unstable over the years, leading to all that had happened since. Zeus had been possessed of fear, paranoia, and treachery - leading to his obsession with killing Kratos, and using his family as pawns in his war.
In the end, even noble Athena finally was corrupted in death. Her ghost unable to resist being possessed by greed, selfishness, pride, and hunger for power.
Realizing he does indeed have the power of Hope, Athena again demands Kratos return it to her. Rather than let Athena have it and let her use it to enslave the world, he kills himself and releases Hope into the world (or at least tries).
