If you try to delete large folders with explorer it could run for several minutes. Also when you try to suppress the moving to recycle bin via SHIFT + DEL.
From all variants to do this, rmdir in command prompt is my favorite
rmdir /s/q <foldername>
btw: deleting of files with good old DOS-del is also a fast way – particularly when you redirect the output:
del /f/s/q *.* > nul