Unobtainable Pokemon

As the Pokemon Company continues to add more and more Pokemon into the Poke Universe, less and less Pokemon seem to be available, compared to the growing National Pokedex, within the game. And actually, this is more truthful than you know within the Seventh Generation. You see, if a Pokemon isn't in the entire Alola Pokedex, odds are it isn't found within this game. There are almost four hundred older Pokemon that cannot be found within in-game (including just about every Legend from previous generations)!

A Full List of Unobtainable Pokemon Can Be Found Here

This means that more than ever before, players will have to rely heavily on transfer Pokemon through Poke Bank, the only way to get all there older Pokemon from older generations to both Pokemon Sun & Moon. Yet even that might not be enough to complete your National Pokedex; players might still need to seek Trades to fill the many holes that might persist.