Oh, that boring Safari. :/
Catch all non-event Pokémon to complete the Kalos Dex. In case you're not aware which are event Pokémon, please have a look.
Mew
Celebi
Jirachi
Deoxys (XY only; can be captured in ORAS)
Manaphy
Phione
Shaymin
Darkrai
Arceus
Victini
Keldeo
Meloetta
Genesect
Diancie
Hoopa
Volcanion (Yet unreleased event Pokémon)