Originally Posted by Fat PK Gaming
As an aside, that dark sub-typing literally does nothing for him in OU.
I beg your pardon? The dark sub type is great for him in OU. As already said, it allows this special attacking dragon not to me murdered after firing off a Draco Meteor thanks to that resistance. Even neutral-Salamence doesn't like taking them, but Hydreigon has no problem. It also allows it to absorb a Shadow Ball from random things that carry it like Gengar, Reuniclus, and Alakazam. This forces those three to rely on the shaky Focus Miss if they want to actually do damage, which has garnished me a win several times.
Also, Dark subtype means that it gets to use the great Dragon resistances without a lot of drawback, unlike Dragonite and Salamence losing their electric resist and amplifying the ice weakness.