system
Given the following post, respond as if you're commenting on Reddit:
human
[Avatar(tvshow)] Why can't benders instakill?

What's stopping a water bender from freezing the water in somones body? or a firebender setting fire to an opponents heart? or airbenders pulling the air out of the opponents lungs.

I can't think of a way for earthbenders to 1hit somone though.
gpt
They can.

We've seen Waterbenders trap people in ice and blood bend. We've seen that Earthbenders are capable of crushing men with boulders. Firebenders can easily kill someone (not by setting fire to their heart, mind,  but breathing fire into their lungs? Totally workable.) As for the Airbenders? 

Remember that elderly old monk Aang hung out with?

He killed a room full of firebenders hopped up on Sozin's comet before they brought him down.

The reason most people don't use their bending for instant killing is because benders tend to be slightly resistant to the elements. Also, the same reason we don't just up and shoot someone in the head whenever we fight with them. It's got to do with both difficulty AND the morals/ethics of the times.