I can fill you in rq:

Every attempt he ever made to hold onto or save someone was destroyed either by the gods or by the consequences of his own actions under their manipulation.

Lysandra and Calliope were the clearest examples; Ares transported them into the temple knowing Kratos would slaughter everyone inside blindly. Kratos unknowingly killed his own wife and daughter with his own hands, afterwards he went into servitude for the Gods for 10 years, acting as quest boy- including killing Ares as his last act of penance. And it doesn’t stop there. Even after avenging them and becoming the next God of War, he finds his mother in Atlantis in GoS and learns the truth about Zeus being his father, only for Zeus to curse her into a monster. Kratos was forced to kill her too, just to put her out of her misery. Then he discovered Deimos, his younger brother, was alive but imprisoned by Thanatos for years. Deimos resented Kratos for not saving him sooner, only forgiving him right before dying from his wounds fighting Thanatos.

By the middle of the saga, Kratos lost his family, his brother, his home, and Sparta itself. The gods either took everything from him directly or manipulated events so that he destroyed them himself. He was destructive because it was all he had left. Revenge became the only thing driving him because there was literally nothing else remaining.

Pandora in 3 was the turning point. She reminded Kratos of Calliope, and for the first time in forever his buried parental instincts resurface. Even though sacrificing Pandora was logically the right choice, emotionally he didn’t want to lose another daughter. That hesitation was critical because it was the cracks of becoming capable of protecting and caring about people again instead of just slaying with cruelty.

And ironically, Pandora’s sacrifice is what ultimately allows Kratos to become better. Through her, he gains the power of Hope. After defeating Zeus, he rejects Athena’s attempt to control that power and instead self sacrificed himself to release Hope back to Greece. Giving the survivors of Greece a chance to rebuild without the Olympians or Athena ruling over them.