This command kills the current empire.
The kill_country command in Stellaris is used to instantly destroy the selected empire.
When you select a country and execute this command, said country's empire is immediately eradicated from the game.
In Stellaris, cheats are executed from the command console, a text box that you type commands into.
To open the command console press the ~(tilde) key, which is typically located under ESC (escape).
If your keyboard does not have that key, or pressing ~ does not work, try the following keys:
Type your command into the console, and then press ENTER .