Ash and Pikachu between them have never really had a 'friends breakup/argument' episode since the very first one have they? Though in fairness besides that, Ash has had conflicts or instigated dilemmas based on his vices in SM, while Pikachu has always had the Pikachu shorts to show his own star power. Between them they are maybe not quite rounded, but individually they demonstrate character ability.
I do find it interesting how SM plays more and more off the fact Ash and Pikachu are almost the same character in different species, being ever eager, agile, spacey and curious and a bit of a doormat due to how hopelessly altruistic they are, likely to play on the whole Z Move bond thing. The episode Lillie took Pikachu home, he practically did all the same stuff Ash did last time he was around.