If that Pokébeach rumor is legit (and I believe it is; he got Fairy-type being SE on Dragon, Helioptile and the others' names AND Sky Battles right), then Fairy is:
Immune to Dragon;
SE against Dragon, Dark, Fighting;
NVE against Fire and Psychic;
Resistant to nothing.
Meaning Latios is one of the few Dragons neutral do Fairy and Hydreigon suddenly gets a nasty 4x weakness. The poor thing.