Board Thread:Speculation House/@comment-34633327-20171002160810/@comment-34633327-20171031022307

Lord Jaric wrote:

Case and point Cinder's seemingly pointless execution of Pyrrha, she had already won the fight but she went ahead and kill her anyways. Except it wasn't pointless. Pyrrha's aura may have been depleted, but given time it would regenerate. Once it did, Pyrrha's Semblance would be a major obstacle to Cinder, seeing as its magnetism in an area surronded by nothing but metal. Killing her prevents something like that from happening.

Even discarding that idea, there is the fact that leaving her alive would have made it likely Pyrrha could have called for help (Cinder had no idea if Pyrrha had her scroll on hand), tried a sneak attack using a piece of scrap metal, or be found by someone and risk them learning about it.

So pragmatically and strategically, killing Pyrrha was the right move, if morally wrong.

Again, keep in mind the only reason Cinder lost was because RWBY's SEW powers awoke with Pyrrha's murder. If Pyrrha had been left alive, the powers would be unawoken, and Cinder would have continued to dominate the situation until Qrow, Ironwood, and Glynda showed up, and seeing as she killed Ozpin, there is no guarentee they could beat her, especially with a liability like Qrow's semblance in affect. If Pyrrha had been killed and Ruby didn't witness it, Cinder still would have dominated it. The only reason Cinder really killed Pyrrha was because the writers had written themselves into a corner, and needed a way to get out of it by creating the SEW. Even if Pyrrha was always planned to die, they specifically did it in this situation so as to enact a Deus Ex Machina, otherwise Logically, Cinder would have won completely. And the fact it was Pyrrha's death that awoke it is an even bigger Deus Ex Machina, as Ruby had very little interaction with Pyrrha in the season, letalone the series, and witnessed the death of Penny, someone she was arguably closer to, and found her sister disarmed (I'm not trying to be funny), yet neither awoke the SEW powers.

TL;DR In series Pyrrha's death was a proper strategic move on Cinder's part since leaving someone with Magneto Powers alive in an area filled with metal ready to use once they heal even a tiny bit it is stupid, but out of series was to enact a Deus Ex Machina that still reeks of sloppy writing.

........ Oh god I think I just paraphrased SomeoneYouUsedToKnow's opinion on the matter. If you are reading this Someone just know I agree with you now in full in regards to the SEW powers and Pyrrha's death.