Q: Safari won't force quit

Try a force restart or shutdown...

OS X: Using the power button - Apple Support

Use the Activity Monitor app in your Applications/Utilities folder and kill it

Safari Corruption       See post by Linc Davis

I have met this issue before but found a useful article from the internet. You can try to follow and learn some useful methods to force quit apps on Mac OS X.

Article: How To Force Quit Mac Apps In Mac OS X

It seems that the link I provided was broken. Just updated with the new one as no way to edit the post.

I have met this issue before but found a useful article from the internet. You can try to follow and learn some useful methods to force quit apps on Mac OS X.

 

Article: Force Quit Mac Apps In Mac OS X