By having them live effectively.

Number one rule. Look at any character that you super enjoyed/loved and were sad to see them die.

Now take a look at disaster movies where literally millions die

It’s almost desensitising enough, it’s because you don’t care about them. They don’t mean anything to you. When a character has a memorable life, having them die (or seemingly die!) is their end of the story.

Every NOO!!, …bang, …rosebud, don’t you know you’re all my very best friends?, …daisy, tell me about the rabbits, George, …the rest… is silence… has led up to this point.

The story ends for them.

If you’re making a character to simply kill them, then you might be doing it wrong.

You are going to die in a fire.