I loved this episode a lot! To me, the driving force of the show was the complex relationship between Stella and Spector and we finally got the pay off of seeing them interact face to face. Her goading him with the red nails during the press conference, their brief run in in the hallway, him breaking into her hotel and getting to know her better than anyone else on the entire show by reading her dream diary. It was what fascinated me the most and getting to see them in the same room was really satisfying!
The nature of their relationship was always ambiguous to me but I think it finally clicked together in a really surprising way this last episode. I always felt that Spector viewed Stella as a mother figure, therefor a potential or ultimate victim. In the end, after their interaction, I think the real dynamic between them is Stella as a daughter figure. There were constant cuts between Stella and Olivia in the scene where Spector sees her for the last time, same hair colour, often the actresses had their head at the same angle.
The fact that she is the only woman that Spector seems to have any respect for, other than his daughter ("I'll speak to Stella and Stella only"). He seemed so relieved to talk to her, finally be himself and explain his true world view to someone he thought his equal. It was great to see Jamie Dornan finally let some of this built up tension out, he had played Spector so restrained the entire series I almost didn't believe he was capable of the crimes until his interview with Stella and he started to show his true nature.
Also, his jabs at her for preoccupation with her father, wanting to have sex with him or having been molested. She seemed really shaken by him saying this, I think there was some truth there. Her diary was proof that he was the only man she is interested in. Him and Spector! Finally how she holds him in the end. Her expression seems like she's clinging desperately to a father figure, his as though he's looking up to someone much younger, how he looks upon his daughter.
I feel like there were a few hints earlier in the series as well, when Olivia says she wants to marry her father out of the blue. Kind of an odd thing for a child to say. Perhaps a foreshadowing to Stella's odd relationship with her father? I think Stella's daddy issues were really at play in this relationship and that's how I see her and Spector's back and forth in the end. At the very least it's how he finally got the upper hand over her, if it can be said he did that. I'd be interested to see how Stella's strong steely character perseveres after all of this trauma. Although I know she'll be back on top somehow as she is one bad ass detective.