Monster Zero x SciFi Japan - Archive Only

I'd say the Black Scorpion (i.e., the largest one in the movie of the same name) easily takes the giant spider.
With its stinger and an armored hide that withstood point-blank fire from tanks, the scorpion seems to have the advantages over a spider that was easily destroyed with one bombing run.

I dunno I think the ants from THEM could take on almost any other eath bound kaiju simply because of their shear numbers.