[@akje]
Depends on where you his them. the plated armour is immensely tough. They use a combination of rare materials to reinforce the hull, and nothing short of an AP canon could even damage it. However, all armour has a weak point. The joints and engines and tracks, that's where you can deal the most damage. A well-placed shot could easily disable a modern tank's weaponry, or it's movement capability. 

Of course, those are just the guns Kami's giving to the boring old humans. He himself has the strength to equal an Oldblood, and as such can handle a far more badass gun.

I'm thinking of effectively giving him the aforementioned Tank Canon, with a scope taped to it. Or potentially a high-powered Railgun, like they're using on some Battleships. Although that would require an insane amount of power. Far more than any battery he could easily lug around. It'd have to be a stationary weapon.