How to delete rows from a SharePoint list using PnP PowerShell?

You can delete a list item/row using below command:

Remove-PnPListItem -List "Demo List" -Identity "1"

Where -Identity is the ID of the list item, or actual ListItem object.

Microsoft Official Reference: Remove-PnPListItem

If you want to remove all items from a SharePoint Online list then check below reference:

Remove all items from a SharePoint Online list using PnP PowerShell

Additional Reference: Get-PnPListItem – Using this command first you can fetch the list items (single item or multiple items) and then you can delete the list item using above command.