How to delete a non-empty directory in Terminal?

rm -rf myfolder

It deletes all files and folders contained in the myfolder directory.

Add sudo at the beginning of the command :

In case user doesn't have the permission to delete the folder:

sudo rm -rf myfolder

Otherwise, without sudo you will be returned permission denied. And it's a good practice to try not to use -f while deleting a directory:

sudo rm -r myfolder

Note: this is assuming you are already on the same level of the folder you want to delete in terminal, if not:

sudo rm -r /path/to/myfolder
FYI: you can use letters -f, -r, -v:

-f = to ignore non-existent files, never prompt
-r = to remove directories and their contents recursively
-v = to explain what is being done