I mean, I'd assume their durability scales to their output given that they literally speak to each other with the force of a supernova.Pretty sure nothing short of an entity is any threat at all, and even that varies depending on their durability
Behemoth's an Endbringer, not an Entity.The problem is wildblow is dumb and Behemoth? can somehow be killed by far weaker attacks by "transmitting the energy through its body to hit the core" or some nonsense
EDIT: although now that I think about it, Behemoth could just be weaker than the others