These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: The Red King is easily in the running for most evil character in the series.
Fridge Brilliance: Fighting the Red King, Harry's first target is the Red Court progenitor's eyes. This is the same tactic he'd used on the White King back in Blood Rites, so no surprise that he'd expect it to work.
One-Scene Wonder: There is Donnar Vadderung, otherwise known as Odin. He gets a single chapter with dialogue and briefly appears at the end but he effectively comes off as a divine David Xanatos.