Problem

A package will not seem to delete using packagemanagement. May complain that it has elements locked by other users.

Solution

Try using developer to right click-unlock. Then try deleting.
If that still doesn't work, try a "hard delete" in package management.
That doesn't work, dry disabling then deleting the package.
Last step is to shutdown the Integration Server then move the package's folder out of the packages directory.

Do not attempt to do this with Wm* packages, they may be critical (e.g. WmRoot, WmPublic etc)