User blog comment:A Living Person/5th Character Sheet/@comment-24350816-20141221003818/@comment-4867780-20141222220631

In the darwinian sense, "strength" is simply about coming out on top. Whether it is power, tactical skills or manipulative cunning, the means just don't matter and anything goes as long as you're victorious (as shown by Esdeath's respect for the Prime Minister's ruthless political skills). As her dying father told her, "victory" is the affirmation of one's strength while "defeat" is the irrefutable proof of one's weakness, making no excuse for his own defeat even though he only lost to overwhelming numbers ("it just means I was weak"). He did notice early that she was a merciless natural killer, but saw it as an edge rather than a flaw, as it clearly increased her chances of survival.

So for all her irredeemable nastiness, you can't reasonably blame her for being what she is, being born a natural sociopath and growing up among hardcore strength-worshippers, where one's suffering are genuinely considered the product of their own weakness.