Mmm... My choice would probably be to take on a Dune sandworm with characters from Final Fantasy 7 remake. Since Final Fantasy characters are kind of used to taking on Mini bosses and bosses that are big and scale I feel like it would be a piece of cake.
Since Dune Sandworms look to be native to sand/desert areas I feel like it would be smart to have the opposite of that. Going by that logic that means I would be equipping ice Elemental related materia just to be on the safe side.
I would first steal the Buster sword from Cloud and ditch him at the Honey Bee Inn. I would probably also "barrow" Shiva as a summon from Coud as well. I would also be taking Tifa, Aerith, and Barret with me.
I would have Aerith on healing support. Barrett would be rapid-fire shots on more mid to longer range support. While Tifa and I would be up close.
Most importantly once job is done we would all head to the Honey Bee Inn for celebration and watch Clouds performance.