remember kids, Synchronize only works 50% of the time.
"From Pokémon Emerald onward, if a Pokémon with Synchronize is leading the party (even if fainted), any wild Pokémon encountered has a 50% chance of having the same Nature as the Pokémon with this Ability. Starting in Pokémon Omega Ruby and Alpha Sapphire, if a Pokémon with Synchronize is leading the party, gift Pokémon (except Pokémon obtained via Mystery Gift) in the Undiscovered Egg Group will always have the same Nature."
http://bulbapedia.bulbagarden.net/wiki/Synchronize_(Ability) 
