When challenging the Galarian Star Tournament, you will eventually have the choice between seventeen different trainers to Pair with or face off against. No matter whether you pair with them or they oppose you, their Pokemon teams will never change. One of these seventeen trainers is none other than Melony (if playing Pokemon Shield), the sixth Gym Leader, and she will always bring into battle Level 72 Mr. Rime, Level 73 Galarian Darmanitan and Level 74 Lapras that will be able to Gigantamax.
No matter what Pokemon you use, it would be smart to have higher leveled Pokemon when facing the Galarian Star Tournament. Because Melony specializes in using Ice Type Pokemon, her Pokemon are especially weak against Steel Type Moves and Rock Type Moves. With all of that said, however, it really doesn't matter what Pokemon you use as long as they are at incredibly high levels. As long as your Pokemon aren't weak to certain other Pokemon Attacks, a Level 90-100 Pokemon will usually handle any Level 75 Pokemon with ease.