How can I delete multiple duplicate contacts in iCloud at once while in browser in Windows?

I exported my contacts from Gmail and Outlook and got them into vcf format and into iCloud (on a Win PC). Looked great at first, then discovered iCloud missed many of the contacts on the import and is now duplicating a bunch of the ones that were there. Presents no options at any stage to deduplicate. All online suggestions I can find all recommend a 3rd party tool (which of course will collect all my contacts). I need to clean up this mess. Any genius ideas for how to dedupe these contacts and get the missing ones back in there without hours of manual work? (I have 700+ contacts). THANKS SO MUCH.