Poison, because it is easy, and because she is good at it. Poison is not as much about the methods and means as it is about keeping one’s expression under control and having a solid alibi. These are skills she masters before the times-table, every time.
(Sometimes she is understood--which is not the same thing as suspected--to have had her hand in the matter. Sometimes she is called the Poison Queen, although rarely to her face. The hero is not always to be found, after all. Entire seasons of history rot on the vine with no one to tend to the kingdom. There is usually a thief and only sometimes a hero, but there is always a princess, and without them she grows into a Queen to make one’s blood run cold.)
A knife, flashing out of the dark of his bedchamber. The knife is wielded by her bodyguard.
A knife in the hand of a hired assassin, to whom she has delivered all of her mother’s jewels as payment--that being the only form of wealth she can access, with the rest of the country’s treasury sunk into her father’s pleasures. (Later, her bodyguard’s knife preserves both his silence and her mother’s honor.)
An angry mob, which is only partly her doing.
A pillow held over his face in the night by a red-haired woman he dragged to his bed, which has nothing to do with her at all. She hates herself the most when she condemns the woman to death.
An accident met while riding far from home, in a grassy field. His horse shies at a bird, released from a snare under its hooves. By the time his manservants arrive on the scene, she is sobbing over his crooked body and the snare is nowhere to be found.
A coup, led by a courtier who hates her and her family and all that she stands for.
A coup, led by a courtier who loves her, and that is strangely harder to achieve.
Poison, spread liberally through the cups of friend and foe alike, because sometimes she does not care.
A prayer to the gods she adores, which sweeps him away with a heart attack as he mumbles his way through an insincere ritual of preservation.
(Once, she begins to love him, looking at him through the lens of pity. She has damned her own country as many times as he has, after all, though he has never lived long enough to see it. He is always dead before she reaches her majority. She has scared herself. That time, she prays that he might be spared--that she could learn to guide the country she will inherit with a gentler hand--and her father chokes on the small bones of a pheasant and dies before the dessert course is served.)
Magic. The cost is so high that she does not try it again.
A fire in his chambers, no doubt set by the pipe he likes to smoke as he reads in bed. She shares his love of books. When she was younger he would read to her from his favorite volumes of history. At the funeral, she puts her fingers to her face to smell for tobacco.
A knife clutched in her own sweaty, ice-cold fingers once, when all else is gone wrong and she has no other tools to use.
A coup led by a foreign king with eyes like candles, who salutes her with the bloody blade with a smile full of strange mirth and stranger understanding.
(He is the only one who calls her Poison Queen to her face, and receives from her only a wry returning smile rather than a bitter drop in his winecup.)