The pool scene from Gideon the Ninth. Especially Harrow’s quote.

I have tried to dismantle you, Gideon Nav! The Ninth House poisoned you, we trod you underfoot—I took you to this killing field as my slave—you refuse to die, and you pity me! Strike me down. You’ve won. I’ve lived my whole wretched life at your mercy, yours alone, and God knows I deserve to die at your hand. You are my only friend. I am undone without you.

It hits so hard, and then somehow even harder on the re-read. This whole book has so many tonal shifts in the prose and dialogue that swing so well between makes-you-snort comedy to that weird stilling in your heart.