Valkyrie forcing her way into the Faceless One's dimension to rescue Skulduggery in the fourth book. Determinator at its finest.
Valkyrie kills a God in The Faceless Ones and owns the others with Necromancy. Which she had never studied before.
"Get away from my ex-girlfriend, you moany little whinge-bag." You tell that sad little emo git, Fletcher Renn.
Fletcher is generally good at chewing people out. His What the Hell, Hero? to Valkyrie was equally awesome.
"Well done, Val. You share the emotional range of a dead man."
Villainous example. Eliza Scorn utterly outplays Magnificent Bitch China Sorrows. She foils her plan to end the Church of the Faceless Ones and takes away everything she holds dear. When she says "Finished with you? I haven't even started." she bloody well means it.
Argeddion and Darquesse are the two most powerful individuals in the universe. They are, to all extents and purposes, basically gods. But they are gods who still have human bodies and human brains, so it turns out Skulduggery can still beat them. Both. Simultaneously. With science. Specifically, he induces an epileptic fit using a particular rhythm of flashes he had memorised some time ago.
Skulduggery's Papa Wolf tendencies towards Valkyrie are a little heartwarming, a little awesome and more than a little terrifying, but the way he deals with Sult takes the cake. He doesn't even have to threaten him.
Skulduggery: I know that you're not about to strike my partner.
His threat to Nadir was glorious.
Skulduggery: You've heard the stories about me.
Skulduggery: Well, the stories are nothing compared to the truth, and the truth is nothing compared to what I'll do to you if Valkyrie gets hurt. I'm the worst enemy you could ever make, Silas. Look at me and answer honestly. Do you believe me?
Stephanie: I get that you hate me. Of course you hate me. I've done horrible things. Not as many horrible things as Valkyrie, but still.. But that's not why you hate me. You hate me because I'm not her. And it's fine if you want to continue like that. Then whenever you hear that I've done something good or nice, you can pretend to be surprised, because everyone knows you think I'm nothing but the evil version of Valkyrie. But I'm not the evil version of Valkyrie. Valkyrie is the evil version of Valkyrie. And now that I'm real, now that I'm a real person, I'm not going to hurt anymore innocent people. Can she say the same?
Skulduggery: I'm going to get her back.
Stephanie: How? You have no idea, do you? You're terrified that the next time you see her you'll have to kill her, because you'll have no other choice. So you can say all the mean things you want. It doesn't bother me. You're just scared.
Skulduggery curb-stomping the Black Cleaver using Necromancy. Without his armour.
Darquesse casually taking out an army.
China Sorrows getting back at Eliza Scorn by leading the people trying to kill her to the fancy new church.
She also goes from losing almost all her resources and allies to Grand Mage of Ireland in a year.
Finbar Wrong in Last Stand of Dead Men. He sees the assassin coming. He sends his wife and child away and cancels all his appointments. He then puts a poisoned tea cup into the man's hands. And calmly informs the dying man what he has done. Do not mess with a Sensitive.