Not to state the obvious, but God of War is a bloody series. Characters murder and dismember each other in the most gruesome ways since Mortal Kombat. As shocking as that sounds, it only scratches the surface of the brutality.
What's more haunting is how far those characters are willing to go to achieve their goals. God of War has some truly despicable people even by that standard. By their actions, one would guess they haven't a shred of human decency. Good thing they're technically not human.
7 Cronos
The one who begins the cycle of sons killing fathers, this Titan fears a prophecy of his children overthrowing him. Therefore, he imprisons them in his stomach. Yeah, he eats his own kids.
That's disgusting in itself, but it's made even more so by the manner in which he does it. Cronos comes for his offspring as infants, essentially ripping the babies from their mother's arms. As evil as this is, it doesn't put Cronos at the top of the heap. After all, it comes from fear rather than malice.
6 Persephone
This goddess is understandably angry. She was betrayed by the other Olympians and forced to live as Hades's wife in the Underworld. However, her method of ending that unhappiness is positively unhinged. She intends to destroy the pillar that holds up the world, thereby wiping out all of existence. That also goes for the gods, herself included. It's a surefire way to stop her pain.
Unfortunately, it also puts countless innocents in the crosshairs. Destroying the pillar will obviously annihilate the mortal realm, snuffing out billions of lives. In conjunction, it crushes the land of Elysium, filled with those good souls who earned a peaceful rest in the afterlife. Persephone is willing to take that away for the sake of vengeance. That takes collateral damage to a new extreme.
5 Ares
The original Greek God of War, Ares certainly lives up to such a title. In that, he lives for battle and conflict. There's not much more to him. Ares prizes violence above all, believing the only value comes from executing that violence.
That's why he makes Kratos his servant. He recognizes the Spartan's talent for ending life and uses him in countless murderous missions for warfare's sake. Sadly, his most heartless act comes when he tricks Kratos into murdering his own wife and child. The God of War surmises that his servant will grow stronger without his pesky family holding him back. Here, it becomes painfully clear that basic human connection eludes Ares.
4 Kratos
Ares's successor turns out to be even more merciless. Many people have wronged Kratos, but he always visits it back on them tenfold. The Ghost of Sparta slaughters his enemies in the most brutal ways possible. These range from ripping them apart to pounding their skulls into a paste. When he gets going, he becomes downright animalistic.
That single-mindedness often impacts others. As the God of War, he targets Sparta's enemies and tramples them under his foot--figuratively and literally. However, that's nothing compared to his conquest of Olympus. Killing the Greek gods causes elemental disasters of biblical proportions.
To be fair, Kratos later repents these actions. The 2018 entry sees him in seclusion, raising his son to be more responsible with his power. He also tries everything in his power to avoid conflict with the Norse deities. He knows firsthand how catastrophic an errant god or unrestrained warrior can be. As much as he'd like to, he can never erase the monster that he was.
3 Odin
Knowledge is power. The Norse god Odin believes his own acquired knowledge gives him the right to rule. Essentially, he's the insecure kid who thinks he's the smartest one in the room. He basks in his followers' love yet severely punishes anything else due to his own paranoia.
This leads him to strike out at anything threatening his "divine dominion." That response comes in both big and small scales. In the former area, he wages war on the other realms, using whatever underhanded tricks he can to bring them under his thumb. On a more personal level, he traps Mimir in a tree for daring to question him, torturing the poor guy every single day. These deplorable acts must mean Odin has the most fragile ego in all nine realms. Moreover, he's the furthest thing from the enlightened individual he purports himself to be.
2 Zeus
Cronos's son continues the aforementioned cycle, becoming the author of Kratos's misfortune through his own fear. Though Zeus raises the Spartan to godhood, he swiftly takes it away when Kratos doesn't display absolute loyalty. He then brutally executes the warrior. Like Cronos, the terror of his offspring drives him to draw first blood.
However, Zeus ultimately emerges worse due to his deeds to others. To begin with, he wages war against all Titans just for the sins of his father. This is despite being rescued by one of those very Titans: Gaia. He truly has no concept of gratitude or loyalty. He further proves that by destroying Sparta purely out of spite for Kratos and beating Hephaestus for a perceived failure. To add insult to injury, he imprisons the latter's daughter in a labyrinth. It seems Zeus turns his wrath on anyone who even looks at him wrong. This somehow makes him even more of a sanctimonious despot than in Greek mythology.
1 Athena
For all of Zeus's faults, at least he sometimes does his own dirty work. Athena pulls strings from behind the scenes, and she does this with no one more than Kratos. She may have some empathy for the Spartan, but that doesn't stop her from using him as a personal hitman. She saves him as a child from Ares, knowing that he'll eventually kill the God of War. In the process, she condemns the Spartan's frightened brother to eternal torment. However, this is just the start of her manipulating the scenario for her own ends.
Not only does Athena facilitate Ares's demise, but she eventually turns Kratos on all her fellow Olympians. She engineers the deaths of her godly brethren to attain ultimate power. Her self-proclaimed wisdom makes her the obvious choice to rule, after all. Everyone else's pain is a necessary stepping stone. She sacrifices those pawns without a care in the world, feigning benevolence along the way. Athena is truly the most cold-hearted character in the God of War series, possessing all the worst qualities of a villainous deity.