Press Command + Option + Esc
Select the app
Click Force Quit
Click Force Quit again if prompted
Click the Apple menu
Choose Force Quit
Select the app
Click Force Quit
Open Activity Monitor
Select the app
Click the Stop button
Choose Force Quit
Use the Dock
Right-click the app icon
Hold Option
Click Force Quit
Use Terminal
Run `killall AppName`
If needed, run `sudo killall AppName`