“I Have No Mouth, And I Must Scream” by Harlan Ellison
Back in my day, we didn’t have Black Mirror to send us hurtling headlong into existential catastrophe. Instead, we had short stories. Mostly, we had “I Have No Mouth and I Must Scream” by Harlan Ellison. BUCKLE UP.
Basically, the world has become a post-apocalyptic wasteland because of a super-computer—one that gained self-awareness and committed mass genocide against all but five people. The super-computer exists only to cause suffering, so it spends all of its time torturing the remaining survivors.
In the end, the narrator of the story—a survivor named Ted—manages to mercy-kill the other four, freeing them from a life of agony. The computer stops him from killing himself, however, and instead turns Ted into a mouthless blob that can do nothing but think and feel. As the last human alive, he is now the sole victim of the computer’s compulsion to torture, and will remain so for eternity. Ted caps the whole thing off by saying, "I have no mouth. And I must scream," at which point I usually consider throwing my laptop out the nearest window and living in the woods like my ancestors of yore.