Shadao
Aim to be a Pokémon Master
My point is greninja isn't his Pokémon anymore. He released it.
I personally feel only pokemon he actually has can count
He released Poipole in SM, and yet the Pokémon came back almost unexpectedly and it rejoined Ash's team just in time for the final 6 vs 6 battle.
The world of the anime, any Pokémon that Ash has ever owned can come back to his team no matter how contrived the circumstances may be.