The Expanse's ending kills enough people onscreen, but the final episode also confirms two major characters are destined to perish in the very near future. If you like your main protagonists still breathing by the time the curtain falls, The Expanse season 6's final installment is the ending for you. Plenty of blood was spilled, but most belonged to Marco Inaros' Free Navy villains as they were assailed by aliens while passing through the Ring Gate, or the unseen sci-fi genre legends (including Deckard, Ripley and Riker) who accompanied Bobbie Draper and Amos Burton on The Expanse finale's dramatic railgun assault mission.
Though most main characters walked away from The Expanse's TV adaptation alive, the finale did openly foreshadow a grim fate for Clarissa "Peaches" Mao. After James Holden and the Rocinante crew brought down her father in The Expanse's early seasons, Peaches paid to get backstreet mod implants surgically inserted into her body, bringing on inhuman strength and speed when activated by a trigger in her mouth. Those mods have been slowly killing Clarissa, and a computer diagnosis in the Rocinante's med-bay confirms Peaches only has around 5 years to live.
The Expanse couldn't have been clearer in signposting Peaches' approaching demise, but season 6's finale also seals a second significant character death - this time more subtly. During the opening Laconia sequence of "Babylon's Ashes," Cara Bisset proudly presents her Protomolecule dog-resurrected brother to their grieving parents, who are horrified by his creepy, alien skin and blackened eyes. As Cara's father calls the Laconia military for help, the two siblings go on the run. Xan warns her, "There's nothing you can eat out here... you'll die," but Cara nonchalantly assures him, "It's okay. If I die, the dogs will fix me."
That's the last audiences see of Cara and Xan in The Expanse season 6, and although their future remains unresolved, that parting line strongly suggests Cara does die of starvation or poisoning, and is subsequently revived in the same extra-terrestrial manner as her brother. There's no reason for the line's inclusion in The Expanse's final episode, other than to sow the seeds of Cara's doom in the near future, and her dismissive attitude toward death demonstrates how she's pretty much expecting the dogs will repair her sooner or later. The ominous sibling exchange also aligns with Cara's arc in James S.A. Corey's novels. Mirroring The Expanse season 6's finale, Corey's Strange Dogs novella ends with Cara realizing Laconia's forests were devoid of edible fauna, but feeling assured that death no longer matters thanks to the planet's curious dogs. Brother and sister both return in Tiamat's Wrath, with Cara now exactly the same as Xan.
The Expanse hasn't yet revealed what becomes of Cara and Xan in live-action. The Amazon TV series wraps up with multiple threads still loose, and a catalog of future book teases unfulfilled - exactly what becomes of the Bisset siblings among them. Speculation is rife that The Expanse will continue in some shape or form, but until that announcement comes (if it ever does), viewers can safely assume Cara dies from eating the alien plants of Laconia's forest floor, and is then remade by the Protomolecule repair dogs. Should she ever feature in The Expanse again, Cara will be just as distant and creepy (and powerful) as Xan - a detail that might've flown under the radar compared to the very overt setup for how Peaches dies.