Prince of Thorns

The first in The Broken Empire trilogy by Mark Lawrence. The series is as follows:

Prince of Thorns
King of Thorns
Emperor of Thorns

Tropes used in Prince of Thorns include:

Abusive Parents: Jorg father is a cold, cruel, callous, calculating bastard, who uses his own son for his ends and then switches to plain open murder when the impossible mission he gave failed to kill Jorg.
A Child Shall Lead Them: Jorg becomes a king in the end of the book. He deposes not his father but Count Renar, who ruled an independent country.
After the End: The early mentions of Christ and Plutarch indicate that the story is set in our world. Later on it becomes clear that the events happen after the present time period.
Anyone Can Die
The Archer: The Nuban.
Artifact of Doom: There is a pile of still-usable atom bomb analogues, which Jorg uses efficiently.
Ax Crazy: Jorg, who says this gem:

"You got responsibilities when you're a leader. You got a responsibility not to kill too many of your men. Or who're you going to lead?"

Brainwashed and Crazy: The true reason behind Jorg's Ax Crazy behavior. The spell redirected his desire for revenge everywhere else except its proper target. Since Jorg was genuinely nasty even without the spell, the results weren't pretty.
The Brute: Brother Rike.
Cold-Blooded Torture
Combat Pragmatist: Jorg. He has no honor when it comes to that kind of thing, or at all really.
Dead Little Brother: Little William to Jorg.
Establishing Character Moment: Jorg kills one of his fellow bandits out of annoyance.
Evil Uncle: Count Renar.
The Evil Prince: Jorg is a crown prince.
Evil Versus Evil
Fat Bastard: Burlow.
Freudian Excuse: Jorg went bad when he had to watch his little brother get murdered and their mother raped and murdered.
Gone Horribly Right: When Jorg blows up Castle Red with an ancient weapon of mass destruction, the accompanying poisonous fallout also destroys the surrounding kingdom and its innocent population.
Homage: Jorg was partially inspired by Alex from Clockwork Orange, however, he is far from being a Captain Ersatz or an Expy.
I'm a Humanitarian: Jorg eats from a necromancer's heart on a whim and gains minor necromantic powers.
Improbable Age: Jorg is very precocious.
Jerkass: Jorg can be very inconsiderate toward his fellows even when he isn't murdering them.
The Lancer: Sir Makin to Jorg.
Lost Technology: There is still some left around.
Magnetic Villain Protagonist: Jorg. He also somehow manages to keep people following him even despite his Ax Crazy Jerkass behavior.
Mutants
The Necromancer: There are some living in the tunnels below Castle Red.
Neglectful Precursors: They left stockpiles of weapons of mass destruction lying around... and leaking.
Man Behind the Man: Some magic users act that way.
Rape, Pillage and Burn: Jorg's band's favorite pastime.
Rebel Prince: Jorg, who ran away with condemned men he had freed from his father's dungeon and became a bandit. He was initially thinking of avenging his mother and brother.
Scary Black Man: Played with the Nuban. While he can be intimidating, he is feared and despised out of racism. Otherwise, he also acts as a limited conscience for Jorg, so he is also a very Downplayed Magical Negro.
Stuff Blowing Up: Jorg's plan to destroy Castle Red succeeds beyond all expectations.
Too Spicy for Yog-Sothoth: Nearly at the start of the novel, a ghost tries to haunt Jorg; instead of fleeing, Jorg allows the spectre to see into his mind... and the ghost runs away, since our protagonist can offer worse thoughts than the ghost itself.
Young and in Charge: Jorg became the leader of a group of bandits as a preteen, a few years before the start of the story.
Villain Protagonist: Jorg.
X Meets Y: Clockwork Orange meets The Black Company