SEVENTEEN | TO THE BEGINNING OF THE END
"'You won't beat me, hero,' Santi whispered. 'We're too... Alike--too... Alike. If anything... And I know this for a fact... You'll become me... Not beat me....'" (Pg 249)
"'There's no hero without the villain... Listen-... If I'm your villain in your story, Jay, and you beat me... You--like I already have--will become what you can't forgive... And slowly... You will bring yourself-... To your own demise. You will. And if you, yourself, don't... Your brother will. Just a thought." (Pg 249)
Throughout the novel, Santi uses the importance of family and quotes influential people in order to manipulate those around him. We learn that his success is at the expense of ruining the ones he considers family, including Jay and Braden. However, Santi has a special connection with Jay, claiming that the two are more alike than Jay realizes.
As Santi's "roofied drink" begins to kick in, he flatters Jay with words of admiration and claims that without himself [Santi], Jay will become his own enemy... Therefore, Jay needs Santi.
At the end of the chapter, we learn that Santi was aware of Jay's plan all along, and triggers Braden into literally pulling the trigger, taking Santi's life, as if alluding to the prophecy Santi laid out in the quotes above.