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.
Carol had grown up enough to realise how unpleasant she had been. She had awful self esteem issues... enough to warrant Jerkass Woobie status. And then, just when she's starting to learn magic and get a little more development, she's stabbed by Valkyrie's reflection.
There are some Randian/Objectivist themes, though they're somewhat more subtle.
Landy obviously thinks that the relationship between Bella and Edward in Twilight is dangerous and unhealthy and viciously satirises it.
Or maybe he just finds it absolutely ridiculous.Or dangerous and unhealthy and ridiculous.
Complete Monster: Quite a few. There's Nefarian Serpine, Baron Vengeous, Dreylan Scarab, Dusk, Mevolent, Davina Marr and Kitana's gang (except Elsie). The Faceless Ones make them all look like pretty nice guys.
Crazy Awesome: Skulduggery refuses to give an answer on whether or not he is insane. Making that decision, he says, is the job of a psychiatrist. He is not a psychiatrist; he just punches people.
China Sorrows is a prime example of this trope. And in heels too!
Eliza Scorn. She manages to utterly outplay China in Death Bringer.
Tanith: You are a very cunning woman. Even more cunning than China Sorrows, I'd say.
Narm Charm: A chunk of the series has some of this starting out due to rampant Awesome McCoolname syndrome, though justified because everyone chooses their own name. The names "Valkyrie Cain" and "China Sorrows" sound more like Dick Tracy characters, but they make it badass. And the name Lord Vile sounds really Narm-y... Then you get to the end of Mortal Coil and you see Skulduggery break down at the sight of him.
Red Herring: We know that Darquesse is the true name of Valkyrie. Well, she has the reflection, right? Nope, it's actually Valkyrie herself. And then at the end of Kingdom of the Wicked, the reflection turns evil anyway.
Remnant Tanith and Billy-Ray Sanguine kissing. Valkyrie certainly seems to think so.
Even moreso when you think about it. Sanguine had a very creepy thing for Tanith for a while. Now, he's got an evil, possessed, fully consenting Tanith. God help the poor thing if/when she comes out of this stupor.
On a somewhat more light hearted note, Valkyrie flirts with a guy at the Requiem Ball. What she doesn't realise is that she has his drunk father's vomit in her hair.
Lord Vile sticking his thumb in Darquesse's eye.
The end of Death Bringer has Valkyrie biting that... thing to get it off her while they try to get away from Lord Vile. Even Melancholia stops being mean to her for a moment.
Darquesse gets her jaw burned off in Kingdom of the Wicked.