Sayid's Turn to the Dark

With Sayid and Claire's "heel turn" during the sixth season (as my buddy at work calls it), you literally bare witness to a behavioral change that sees their humanity seemingly removed as if The Man in Black took a scalpel of psychology at cut it all away. Claire doesn't even resemble the sweetheart with a genteel spirit from the first season, replaced with this vicious ice queen while Sayid's weak spot of Nadia (in the sideways off-island, her marriage to his brother was encouraged because Sayid felt he didn't deserve her) is used as leverage against him when he is sent out by Dogen to kill MiB. By the end of Sundown, Sayid has completed transformed as those in the temple once followers of Jacob have gathered behind MiB, while Kate finds herself in a bind due to her purpose in returning to the island (retrieving Claire so she can be returned to her son) in the first place. Miles, Ben (who I would have thought might align with MiB instead of Iliana), Sun, and Iliana leave through the same trick door in the temple as Jack and Hurley, while the black smoke monster lays waste to Jacob's followers (those that didn't agree to choose his lead, messaged by Sayid with forewarning). To fully cement his turn to the darkside, Sayid drowns Dogen and slits Lennon's throat! Dogen spoke of the death and resurrection of his son in negotiation with Jacob who requested in return his devotion on the island. In the end, Dogen and Jacob are dead. This episode could be considered The Empire Strikes Back.