Intelligence is a great help in the evolution-by-survival--but intelligence without muscle is even less useful than muscle without brains. But it's so easy to forget that muscle--plain physical force--is important, too!
West of the Mississippi was Mob territory, a society whose entire system of values was totally opposed to the Syndic. Here morality ruled with an iron hand. When a wave of assassinations broke out in New Your, it was clealy time to take action against the Mob!
It may be that there is a weapon that, from the viewpoint of the one it's used on, is worse than lethal. You might say that death multiplies you by zero; what would multiplication by minus one do?
Because this is a masculine world, the author of this fairytale is usually identified as the wife of Poul Anderson. But a few more incisive cameos of fantasy such as this, and Mr. Anderson may come to be identified as Karen's husband.