My biggest off with this story is that MC has yet to fight himself. It's always his troops fighting. Even though he has SSS class forbidden mage class, we have yet to see him shoot a single spell.
Not only do his classes skills focus on buffing his army (2x Elemental dmg, 5% enemies killed explode on death) the skills of his heroes and effects of his equipment focus on supporting armies as well. Its clear that its better if MC buffs his tens of thousands of late game troops then shoot some level 40 SSS class spells. Rather than 1 man army solos the world, its looking more like the story will take the path of leading a crusade through the demon world with my army of divine T-800s to purge heretics