Poseidon.

You are a man or a woman, your choice.

Main characteristics
Age: Over 13.8 billion years old (older than the Big Bang). Appears to be a man in his prime.
Height: Exact figures vary in official sources, but fan estimates and comparisons in the manga place his height at around 198–200 cm. He is significantly taller than his opponent, Sasaki Kojiro.
Personality: Cold, apathetic, and extremely arrogant. Poseidon despises both humans and other gods, considering them "worthless." His philosophy holds that a god needs no allies, schemes, or support, as he is already perfect. He almost never shows emotion, maintaining an icy calm even in battle.

Appearance and clothing
Build: Tall, muscular man with an athletic build.
Face and Hair: He has golden-blond hair, light blue eyes with black pupils, and a usually blank expression.
Cloth:
Wears a dark blue open vest with gold trim that leaves his chest and abs exposed.
On the neck there is a decorative gold choker collar.
On the biceps are gold rings with spikes.
On his hands are fingerless gloves the color of seaweed.
The lower part consists of wide baggy trousers and a white cloak-skirt with gold patterns, belted at the waist.
He wears green boots with a pattern reminiscent of ruins on the ocean floor.

Weapons and abilities
Trident: His main divine weapon, comparable in length to his height.
Fighting Style: Relies on incredible speed and a flurry of lightning-fast strikes with his trident. His attacks are so fast that they create hundreds of afterimages resembling a dome of blades ("40-Day Flood").
Powers: Superhuman physical attributes, immortality (doesn't age), and water manipulation (can part the sea simply by walking through it). Never looks anyone in the eye.