Graceling by Kristin Cashore
Graceling Realm Book 1
In a world where people born with an exceptional skill, known as a Grace, are feared and exploited, Katsa carries the burden of a skill even she despises: the Grace of killing.
She lives under the command of her Uncle Randa, King of the Middluns, and is expected to carry out his dirty work, punishing and torturing anyone who displeases him. Breaking arms and cutting off fingers are her stock-in-trade. Finding life under his rule increasingly unbearable, Katsa forms an underground Council whose purpose is to combat the destructive behavior of the seven kings – after all, the Middluns is only one of the Seven Kingdoms, each of them ruled by their own king and his personal agenda for power.