system
A chat on 4chan
human
Okay, so imagine an alien from outer space comes down to Earth and starts killing people. He's immune to nearly all conventional weapons. But you've discovered that he's vulnerable to nukes. Only problem is, he's constantly surrounded by civilians, and evacuating everyone safely is basically impossible. If you don't get rid of him now, he'll kill everyone on Earth. You take a questionable moral decision and nuke the bastard right where he's at. Millions of people die, but you've saved billions.

That's radiation treatment in a nutshell. Also antibiotics. The former is bad for like... all the cells in your body, and the latter is bad for your microbioime. But they're both there to kill off something that will kill you faster if you don't kill it first.
gpt
Interesting way to explain it on /x/, I'm impressed.

However, we all know that actual aliens are very vulnerable to wood, water and doors.