Kratos already killed Hercules in God of War III, caving in his skull with the Nemean Cestus — and canon is canon.
This one actually happened. In God of War III, Kratos faces Hercules in the Forum and defeats him in one of the most brutal boss fights in the franchise. Hercules wields the Nemean Cestus — massive lion-headed gauntlets — and is physically one of the strongest beings Kratos ever fights. The ground buckles under their blows, pillars shatter, and the arena itself crumbles.
Mythological Hercules completed the Twelve Labors, killed the Nemean Lion with his bare hands, held up the sky in Atlas's place, and is a demigod son of Zeus with strength that borders on limitless. In Greek mythology, he's arguably the greatest hero who ever lived. He's immensely durable, having survived being poisoned by the Hydra's blood and enduring trials that killed lesser gods.
But Kratos is simply on another level. By the time he faces Hercules, he's already killed Poseidon, Hades, Helios, and Hermes. He's wielding the Blades of Exile, has Spartan Rage on tap, and his combat feats dwarf anything in Hercules's resume. The Twelve Labors are impressive, but Kratos has killed things that would make the Nemean Lion look like a housecat. Their canonical fight demonstrates this clearly — Kratos takes Hercules's best shots, steals his weapons, and beats him to death with his own gauntlets.
Kratos canonically defeated Hercules by tanking his strongest attacks and then beating him to death with the Nemean Cestus. By the time of their fight, Kratos had already killed multiple Olympian gods, each of whom dwarfs Hercules in power. His Spartan Rage and divine weapons give him tools that Hercules simply cannot match, and his combat skill after centuries of warfare is unparalleled.
Hercules is the strongest demigod in Greek mythology, having completed the Twelve Labors and held up the sky. The Nemean Cestus give him devastating striking power, and his durability is legendary — he survived the Hydra's poison and endured feats that killed lesser gods. In raw physical strength alone, Hercules may be the only Greek figure who can match Kratos pound for pound.
Kratos wins definitively — he already did in canon. Hercules is an incredible fighter and one of the toughest opponents Kratos faces, but the Ghost of Sparta operates at a tier above demigods by God of War III. The Nemean Cestus becomes Kratos's weapon after the fight, which tells you everything about who came out on top.
Kratos also fights
Hercules also fights