Which Pokemon can't be legitimately obtained using only the gen 6 games?

Question

Since Pokemon Bank/Poke Transporter won't be able to be downloaded after march 2023, is there any Pokemon that can't be legitimately obtained using only X, Y, Omega Ruby and Alpha Sapphire through catching breeding or evolving a pre-evolution?

Answer 1

If you have all four of those games and the means to do trade evolutions, they're fortunately placed enough to cover everything except mythicals (Mew, Celebi, Jirachi, Phione, Manaphy, Darkrai, Shaymin, Arceus, Victini, Keldeo, Meloetta, Genesect, Diancie, Hoopa, Volcanion--note that Deoxys will be obtainable in the Hoenn games) and Pokemon that weren't introduced until later generations, such as Rowlet.