How to "killall" Visual Studio Code in Terminal?
I have Visual Studio Code, version 1.1.1, installed and on my system the following works for me:
kill -9 $(pgrep Electron)

Update: Just tested with Visual Studio Code, version 1.14.1, under macOS 10.12.5 and the above command closes Code and Code Helper that show in Activity Monitor.
PS: killall Electron also works.