I'm surprised Gilbert is dead. I didn't remember Lindsay, but she showed up back in chapter 158 as well....
Right - Lyndsey's been a long-running character with a number of background appearances, and I'm pretty sure she even appeared in the anime, but I don't recall that she's ever had any significant lines of dialogue.
In a way, it's kind of a shame we didn't get to see a little more from Lindsey to add just a little characterization and chemistry with the regular cast of characters - it would have added even more of a lasting impact for her departure.
Still, an on-screen decapitation was pretty brutal: I guess that's our last hint that the story has "shooed out the clowns" and now we're in for some Serious Business.
We've seen some dark story moments in the past - we watched one of the Belles give up on living and starve to death, we saw pretty rough ends for poor Margaret/Maggie between a throat-cutting and soot depletion from one of Anthony's experiments, and Nicholas work himself to death trying to earn medals, and I'm sure there were a few other such deaths, and those hit hard in their own ways, but that might have been the most graphic death scene yet!
I believe I was just saying in some earlier comments that we really haven't seen much characterization yet for third-floor adults like Great-Grandfather, Dorothy, Sophie, and Ryan, other than Ryan coming across like a bit of a sadist, and Sophie has a creepy taste for soot (a product of shadows' misery!) Well, we still don't know very much about their backstories, but this chapter confirms that Ryan is a sadist and killer, and pretty firmly establishes that Dorothy if fussy about cleanliness, and also seems to be a bit callous about harming the children (it's arguably self-defense, but still, she was more worried about getting her clothes dirty than killing the other characters!) It's a bit late in the story for redemption arcs for characters like these - I think we can take this characterization as a pretty clear sign that Dorothy, Sophie, and Ryan are probably not likely to do heel-face-turns to Kate and Emilyco's side anytime soon!