Task manager should be able to terminate any program. Even clicking any grayed out window several times will prompt by Windows to terminate it.
If you are using Explorer dialogs for copy/move operations then there is nothing I can do about freezing of transfers, explorer also does it all the time dropping the speed to 0 and cancelling never finishes.
Switching to Taskmaster in Settings>Advanced for file operations makes it use a lower level file operations and is more reliable than Explorer's