Even "kill all humans" is difficult to define. Is a human dead if you flash-freeze them in liquid helium? It would certainly make it easier to cut out the canc

Even "kill all humans" is difficult to define. Is a human dead if you flash-freeze them in liquid helium? It would certainly make it easier to cut out the cancer. And nobody said anything about defrosting them later. And even seemingly healthy humans contain cancerous cells. There's no guarantee their immune system will get all of them.