How to Delete Unwanted SharePoint file locked by Owner

In SharePoint go to the library where the unwanted document is locked then discard check out.

To do this, simply right-click on your document on your library or list (or you can also click the three dots beside the file name) and click on More > Check Out.

It will then advise you that you will lose all the save changes to the document go ahead and click Discard Check Out.

You should now be able to delete the unwanted document utilizing the usual methods