The best commentary on Michael's betrayal of Kay, IMO, comes near the beginning of III. Michael, with his usual self-justification fantasy, tells Kay: "I spent my LIFE protecting my family from the horrors of this world." And Kay replies, "But you became my horror." Right on, Kay.
Powerful scene, TB.
Such a shame because Part III DID have its moments. Just a case of the whole being lesser than the sum of its parts.