Crash the entire game

i want to know how to crash my entire game in case of failed loading of resources ?
and how to personalize message or message box for it ?
thank you

This will quit the application:

Application.Quit;

Another solution that is not documented is using:

Application.Suicide(1);

Keep in mind this should NOT be used in the editor unless you saved your project. If you’re curious, it just makes Unity crashes and warns Windows that it “crashed”. The Unity Error Report window also pops up.

You could always throw an exception. This will work in the editor, and will behave very similar to any other error during GamePlay.

Link to documentation