Below is some ways of how to force quit an application on Mac you can use.
If you have unresponsive app on your Mac, you have four ways to close it.
Right-click on the unresponsive icon in the dock and hit the Option key. With Option key pressed, the Quit menu item turns into Force Quit.
You can force quit from the Apple menu. Click the Apple icon in the upper-left corner and choose Force quit that will open Force Quit Application window. You can highlight the troublesome app and click the force quit button to close it.
How to force quit an application on Mac with keyboard shortcut
Press Cmd-Option-Escape to force quit a troublesome program with a keyboard shortcut.
You can force quit the troublesome app from within the activity monitor. Highlight the app you want to close, click the X button in the upper-left corner and then click the force quit button.