I already expressed my thoughts in DMs, but I'd thought I'd say it publicly too: this series is phenomenal. This tale in particular is a culmination of everything in the series; it feels more like a climax than a resolution, but manages to satisfy the story in a way which it functions as both. The fear I felt from the final murder and gaslighting scene was extremely real and primal, but it doesn't overstay its welcome or pull the punches. It hits and it stays.
The themes of the series are also phenomenal, and I'm shocked by how much you're able to get me to like these characters despite how genuinely awful they are. It takes serious skill to do so and you've executed it perfectly.
I couldn't upvote this harder. Thank you for the wonderful and existential-as-fuck read.