There are more then one way to force quit an application in Mac OS X.
You can quickly do it from your keyboard with this simple key command.
Her is how to force quit a application in Mac:
By pressing the “Option,” “Command” and “Esc” keys simultaneously you will open the Force Quit Applications dialogue box.
(ps. the option key can also be called Alt key)
Form here you can choose the app you want to force to quit and click the “Force Quit” button.
TIP: Holding Cmd-Opt-Shift-Esc for three seconds force quits the frontmost application