And while we're on the topic of comparison, since that seems to be a "to do" thing, why not compare her to Keiichi in his two "lol killer loli" chapters? (I am aware this might be pointless but I'll go ahead and do it anyway
) It's obvious Shion was being affected by
something and painfully obvious Keiichi was, and he beat Rena and Mion to death. Did Rena and Mion do anything wrong? No, but that didn't stop Keiichi, because he
believed they did/were going to. Yes, Keiichi thought they were trying to kill him whereas Shion wanted her warped revenge, but I think there's a point in there... somewhere. Maybe.
And then there's in the other arc. True, Keiichi was a lot closer to Satoko than Shion was to Satoshi, and yes Teppei deserved it whereas most of Shion's victims didn't, but it's still murder no matter how you look at it.
And uh, since this is probably one of the worse Shion-defenses (why she needs a defense when practically EVERYONE turns into a psycho killer at some point, I do not know) out there, I'll stop now