If 3rd party is in play... Warpriest + Tiefling + Strong Build (fiendish heritage) + WP Focused Weapon Scaling + Impact + Weapon Storm (3rd level spell that reproduces base weapon damage every 3 levels in the form of a force weapon). Chose something that does high base dmg like a rhoka or great sword / axe and you will be hitting 30 D8 base damage with weapon storm, duration 1/r per level and the ability to recast many times. Rhoka will give you a better crit multiplier and then add keen. For extra absurdity add mythic, take eldritch heritage + mythic EH, bloodline giant to get huge size and by 18 your base damage is now 40 d8.
