TL;DR: run the commands in Terminal:
open -a 'Uninstall iShowU Audio Capture' mdfind -0 'iShowU Audio Capture.kext' | xargs -0 sudo rm -rf -- sudo kextcache --clear-staging
Uninstall
App
Uninstall with the uninstaller app first:
open -a 'Uninstall iShowU Audio Capture'
Manual
Find all the iShowU Audio Capture.kext directories:
mdfind -name 'iShowU Audio Capture.kext'
Delete the kext directories:
mdfind -0 'iShowU Audio Capture.kext' | xargs -0 sudo rm -rf --
Alternatively, to delete the kext directories one-by-one:
sudo rm -rf '/Library/StagedExtensions/Library/Extensions/iShowU Audio Capture.kext'
sudo rm -rf '/Library/Extensions/iShowU Audio Capture.kext'
Then clear the kext staging area:
sudo kextcache --clear-staging
Final
Once you finished deleting, restart your computer.