[Guido]

I feel this is the episode that draws the demarcation point for Kirei Kotomine.

To me the conversation that Archer stirred up to him clearly implied, that the King of Heroes was offering Kirei to take a bite from the forbidden apple.

I'm using forbidden in the context of that which Kotomine sees of no meaning or shape to him. But the offer to spy on the other Masters' motivations might likely or not corrupt Kirei, because I find it too tempting.

On the other hand, I can see the strenous relationship between Archibald and Lancer. I have to say this, but being a Servant chosen in the Holy Grail War is a matter of pure luck because relationships like those of Tokiomi-Archer and Archibald-Lancer clearly show from time and time again that there's no connection of interests where both parties can work from to cooperate actively with each other; I do not forget that most masters tend to view and use their Servants as mere tools, provided that Masters do not go stray from the rules.
Interesting to observe was Kayneth's assistant, Sola-Ui, whom I can see taking a geniune interest to Lancer, though not as a Servant. And she was bold but composed to call on Kayneths' failure to realize that the aftermath of the duel against Saber scored an advantage for the time being which they can exploit against Saber.

Last but not least, is Ryuunosuke. Although I do find Caster a bit of detestable, though the magnitude of his obsession-mania is firing up his murderous rampage by the minute, Ryuunosuke's plain as sick or even surpassing Caster in terms of depraved murder and sickness.
I hold no empathy for that Master, maybe except for Caster who confused Saber with his love, and the historical Jeanne D'Arc, because I admit in his time onscreen in this episode he was comical but still pathetic.