Depends on which starter you chose.
If you chose Scorbunny I would suggest You use Tyrantrum, because it can(probably) tank all of Leon's hits, exept for Dragupult's dragon breath, Haxorus' outrage and earthquake, and Intelion's Mud shot. Tyrantrum can tank Charzaird's hits better than Tyranitar, so it makes a good check to 2 of leon's Pokemon. Just bring a Grimsnarl, because it can take Dragupult, Haxorus, and maybe, by luck, Aegislash. If you think Tyrantrum will be too beat up from Mr. Rime to battle Leon's Charzaird, go for Coalossal. It's practically the same, but different typing. Just remember to save your dynamax for Leon's Charzaird!
If you chose Grookey, you will also want to go for Tyrantrum for the same reasons as before, exept use it against Cinderace and Charzaird, and get a sturdy grass type to tackle Seismatoad. Just bring a Grimsnarl, because it can take Dragupult, Haxorus, and maybe, by luck, Aegislash. If you think Tyrantrum will be too beat up from Cinderace to battle Leon's Charzaird, go for Coalossal. It's practically the same, but different typing. Just remember to save your dynamax for Leon's Charzaird! For an alternative, you can use a Whiscash to deal with Cinderace.
If you chose Sobble, You'll definatly still want Tyrantrum. Rillaboom's grass attacks are gonna make quick work of Tyranitar, so you want a good Pokemon. Also, Tyrantrum can learn a fire type move to kill off Rillaboom. Just go to Hammerlock, grab TM 68(fire fang), teach it to Tyrantrum, and watch Rillaboom go up in flames. Just bring a Grimsnarl, because it can take Dragupult, Haxorus, and maybe, by luck, Aegislash. If you think Tyrantrum will be too beat up from Rillaboom to battle Leon's Charzaird, go for Coalossal. It's practically the same, but different typing. Just remember to save your dynamax for Leon's Charzaird!
Note: Keep all your Pokemon around level 70 or higher for this fight.
