Complex sentence: Kai was a challenging role, as Michael had to breathe life into a character who was essentially dead, uncaring and unmotivated, which he managed to do, despite the inherent lack of range that the role permitted.
Split into simpler sentences: Kai was a challenging role, as Michael had to breathe life into a character who was essentially dead, uncaring and unmotivated. Which he managed to do, despite the inherent lack of range that the role permitted.