This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Fool Moon
The loup garou's rampage through the special investigation department. Especially chilling is the description of the thing going through the cell block, slaughtering prisoners in their cells while the prisoners further up the line are unable to flee and can only scream as they hear it getting closer.
In particular, the graphic and chilling description of one of the police officers dying because he was paralyzed and couldn't breathe. This was a result of the loup-garou having torn his spine out.
Just the Loup Garou in general. Despite not being very big (about 5'5 since it hunches over) the way Harry describes makes it seem more like a hurricane or an earthquake rather then a flesh and blood beast. A pure, terrifyingly powerful (and in a way beautiful) force of nature guided only by mindless, primal fury.
Or, for a more Tear Jerker perspective, imagine being Harley MacFinn on the night of Kim Delaney's death: sensing the circle isn't working, desperately begging her to flee, feeling the frustration at her refusal building up and knowing it's about to get her killed.
Try reading the sequence where Harry starts getting caught up in the bloodthirsty power-rush of wearing Harris's Hexenwulf belt, and then going back to re-read the scene of Parker's death. Then contemplate how freakin' much the trio of Hexenwulfen must have enjoyed ripping the Streetwolf leader to shreds and chowing down on him. Brrrr...