Verethragna is a battle-loving god and is willing to do anything to find a worthy opponent. He even went as far as to revive Melqart just so that he could fight him. He further gave one of his incarnation to Godou to test him and strengthen his opposition.

In the Light Novels, prior to regaining his memories, Verethragna was a kind and gentle figure who loved sports and competing against others of worthy skill.

After he gained his memories back, he became very arrogant and contemptuous of others.

(Source: Campione! Wiki)