Bulky Water types are generally handled by Tapu Lele, yes. Mega Slowbro, Mega Swampert and CM Tapu Fini can't switch into Tapu Lele and only Swampert can KO without a boost, while Lele can in turn 2HKO any of them easily. Truth to tell, Mega Swampert under rain isn't exactly ideal, but rain...