James McAvoy was great, but...
Everyone else's acting was pretty bad. I almost convinced that everyone is actually only McAvoy's hallucination; that he and everybody else is actually one and the same person living in a asylum's cell because of how unnatural these people acts and behaves.
Even the Power Ranger movie has better acting all around (except McAvoy). Split is in the teritory of today's low-budget Japanese horror movie acting! Unfathomable for an American production.
Is this the director's incompetence to lead his actors or they just terrible at acting?