She's never seen Sans like this before. She's seen him upset, and nearly at to the end of his rope, but this a hair's breadth away from violence, and-

And something had to tear that gash in the warehouse wall a few weeks ago, Rarity remembers with a stab of dread. She's betting it wasn't Papyrus, and Sans had been exhausted...

"Sans, that's enough!" She's trying for firm; she lands on fear. It's not good, but it's not enough to stop her either. She grabs Sans' shoulder and holds tight. The last thing they need is for this Mexican standoff to explode into all-out war, and Sans is just unsteady enough to be the one to pull the trigger.