xkill
xkill is a command-line utility for the X Window System that allows users to kill X client processes by interacting with their windows. When xkill is invoked, the cursor typically changes to a skull or crosshairs icon. The user then clicks on the window of the application they wish to terminate. Once clicked, xkill sends a kill signal to the X client associated with that window, usually causing the application to close.
This tool is useful for situations where an application has become unresponsive or is behaving erratically
While convenient, xkill should be used with caution. Killing an application by clicking its window does not