We often see protagonists in a story showing mercy to their opponents, or even lending them a helping hand, but we rarely see them willing to go as far as Karla did.
These may just be some small, simple gestures, but they may just very well make a lot of difference down the line, yet the thought of doing so usually don't even cross people's minds. Now what does that say about our society?
i would also grow a deep abyssal hatred for karla after that. but at the same time knowing that she's most likely the one true dark lord i would be far too traumatized to ever do anything towards her.