Remember the initial setup for the entire story. In the previous novel (Short Victorious War), Young had deserted out of sheer, inexcusable cowardice. Against direct orders. The only people who didn't see, or admit, that Young ordered not just his ship out of formation, but the squadron of other ships he was leading as well, to flee was because of cowardice and panic were his political allies. Young's own first officer saw him, the captain of Warlock, as a coward and deserter.

His ordering of his squadron out of formation, and then continuing to flee the formation against orders to return while the fleet was engaged against overwhelming odds, got Manticorian spacers killed. Warlock's absence weakened missile defense nets. It caused confusion and chaos in the tactical situation. These things are directly responsible for the death of Naval Personnel.

The first section of the story deals with how Young's political connections are shielding him from the consequences of this action. Desertion and cowardice in time of combat is a firing squad offense in the Royal Manticorian Navy. In most real world militaries it is as well. For what he did at First Hancock he was facing the death penalty.

Yet and his political allies abused their power to spare him of this penalty. To the detriment of the RMN and the Manticorian government. One of the reasons militaries punish what he did (desertion in battle) so harshly is the damage it does to the overall fighting spirit of the entire service. When soldiers/spacers know they can cut and run without consequence, some will. It'll happen more often. Which gets people killed. Which loses battles. Which loses wars.

This point is made throughout the trial deliberations as the factions (Navy vs Young's Allies) argue over whether or not Young should be punished (killed). It's not that the Navy wanted Young to die, it's that he needed to because sparing him told the rest of the Navy "desertion and cowardice that gets Naval Personnel killed won't be punished."

After merely being dishonorably discharged, Young hates Honor more than he already did. He resented her previously because he was a noble, and she wasn't. Yet she had a brilliant career, and was getting promoted past him. He was a small, petty man who wanted revenge. He didn't see that his own personal failings were the source and cause of his stalled (and then ruined) career. He just decided Honor was to blame because if she'd never showed up in his life, he would've risen just as a noble should because that's his noble birthright; to ascend and be lauded.

So he plotted to kill her.

When Honor challenged him to the duel, she didn't just say "you killed my lover/friend."

> "My Lords and Ladies, there is among you a man who has conspired at murder rather than face his enemies himself. A would-be rapist, a coward, and a man who hired a paid duelist to kill another. A man who sent armed thugs into a public restaurant only two days ago to murder someone else and failed in his purpose by the narrowest margin." ...

> "My Lords and Ladies, I accuse Pavel Young, Earl North Hollow, of murder and attempted murder. I accuse him of the callous and unforgivable abuse of power, of cowardice in the face of the enemy, of attempted rape, and of being unfit not simply for the high office he holds but for life itself. I call him coward and scum, beneath the contempt of honest and upright subjects of this Kingdom, whose honor is profaned by his mere presence among them, and I challenge him, before you all, to meet me upon the field of honor, there to pay once and for all for his acts!"

Emphasis mine.

Honor used the dueling laws for arguably one of the very purposes they exist (in the story and in real world nations that had them). Young had wrapped himself in political advantage to gain power and avoid consequences. He sought to use his position to abuse and shirk his responsibilities. Dueling was, and is, a way to "even the scales." Officers in England on occasion challenged other officers to duels over the same kinds of things Young was doing, and for the same reason Honor did; to even the scales and impose consequences where the system had failed to.

She didn't just seek revenge for herself, though she definitely wanted that. She also sought revenge for fellow crew members and officers of the RMN. She sought to correct the error of the story's initial tribunal that issued a flawed verdict that spared Young and allowed him to escape the deserved consequences of his action.

He got people killed. They died because of his cowardice. They died because he planned it. They died because he didn't care to discharge his responsibilities as an officer and member of the House of Lords in an honest and forthright manner. They died because he felt his life and his plans for his life mattered more than their lives did to them.

I submit that, if anyone "ever needed killing", Young is on that list.

Honor is not a murder. Young deserved to die many times over. Many. She was justice come knocking. Not just for herself. For the Navy that was too weak to impose it themselves.