why he is not killing them?
anyway, when is segs?
Seggs was last chapter.
He's not killing them for a few reasons. First is that their upper brass would likely use any deaths as casus belli -part of why they were making a big show of executing the scout in the first place, in hopes it would draw an attempt to rescue them, have the rescue look like an attack on their camp to any third parties watching (as any movement of armies would draw attention from other nearby nations, who would work to keep an eye on things through their own means and people), and so on. This is exactly what the halidom wants.
Secondly, vanguard units used for something like this would have to be some of the more elite or loyal soldiers, people who could be trusted not to fuck up and make the kingdom look like the victims, or spill the beans about their intent and confirm what any intelligent noble/politician would suspect (and confirmed within reason by the initial attack on Anko being 'Silver General Spearmenship'). Overpowering them to the complete destruction of morale without a single casualty both sends a message about the difference in strength between them, and instills a deep fear in the soldiers that will spread through the army as a whole as the story is shared and grows. It even helps that Second is using a literal monster for the attack, as Anko's nature on full display will have those guys jumping at every shadow for the rest of their lives.
A third bonus of it being accomplished by just Second and Anko is that officially, the kingdom can deny involvement in the attack, claim it was the independent actions of a adventurer, and while they don't condone it, because it prevented further hostilities, they won't do anything about it either -if they acknowledge it at all. It's likely the halidom would prefer to cover up their army being routed by a single person and their pet, to maintain appearances of their strength both to their own citizens and other nations, and wouldn't press the issue.