Warning: The apps you delete will be deleted permanently without any option to undo it. The only way to get back the app is by manually reinstalling it, that too if it is available online. Deleting some apps like iTunes, Safari, Maps etc. may result in abnormal behaviour of the Operating System. Proceed at your own risk.

Have you ever tried to remove any default macOS app like chess, mail, safari, stickies, photo booth and come by a dialog box that says "AppName.app" can't be modified or deleted because it's required by macOS? 

Well, here is how to delete them permanently.

•  Open the terminal app.
• Type cd /Applications/  at the command line and hit Enter to go to the Applications directory.

• To delete any application replace "AppName" in the following command with the name of the application you want to remove.

sudo rm -rf AppName.app/

• However, if there is a blank space anywhere in the application name, use the following command:

sudo rm -rf App\ Name.app/

For example, if you want to delete the chess app simply type

sudo rm -rf Chess.app/

or to delete the Photo Booth app, type

sudo rm -rf Photo\ Booth.app/

at the command line and hit enter. Voila, the app is gone. You can do this for any app you want to delete.