Try deleting at a Command Prompt in a Recovery Environment. There is an internal & an external Recovery Environment. If the internal one still presents permissions problems, the external one surely will work.
(1) Shift+Restart gets to the internal Recovery Environment (Choose an Option screen).
(2) Click "Troubleshoot > Advanced Options > Command Prompt".
(3) Enter...
RD /S C:\Folder
(4) Exitthe Command Prompt with its "X" or type "Exit".
(5) Click "Continue" to return to Windows.
Notes:
(a) "/S" deletes files in the folder & all its subfolders.
(b) If "Folder" isn't the real name of it & the real name has a space in it,
then enclose the full path & file name in quotes thus: "C:\Real folder name".
If that still doesn't do it, then you must make a win 10 Installation USB drive, boot to it, & select "Repair your computer" (instead of to install). That will get to an external Recovery Environment which surely will delete it.
Here is the Help screen for RD...
C:>RD /?
Removes (deletes) a directory.
RMDIR [/S] [/Q] [drive:]path
RD [/S] [/Q] [drive:]path
/S Removes all directories and files in the specified directory
in addition to the directory itself. Used to remove a directory
tree.
/Q Quiet mode, do not ask if ok to remove a directory tree with /S