Hi ABREALESATE,
Welcome to the Apple Community, where some of us do our best to help each other.
Seems there isn't a method for removing duplicate contacts / merging a list easily.
(I may be wrong ?)
You might want to:
Export a contact as a vCard on iCloud.com: ,
or
You can export all of your iCloud contacts as a vCard and use it as a backup:
https://support.apple.com/en-au/guide/icloud/mmfba748b2/1.0/icloud/1.0
or
If you decide to:
Archive the contacts you store in iCloud via Mac or Microsoft Outlook
https://support.apple.com/en-au/guide/icloud/mmfba74949/1.0/icloud/1.0
OR
Wondering if you might want to start with sorting that huge amount of iCloud contacts to make them more manageable.
There is an iCloud User Guide online that has useful info. on contacts:
Eg:
Sort contacts on iCloud.com
(choose an option from the sort order ... by first or last name if you want to re-order them all.)
https://support.apple.com/en-au/guide/icloud/mmfba74a66/1.0/icloud/1.0
(Duplicates may be evident if they are all sorted alphabetically the same way ?)
You might want to:
Group contacts in some logical (to you) system
(maybe one group might be the duplicates, ready to ignore or delete)
How to create a group of contacts on iCloud.com
https://support.apple.com/en-au/guide/icloud/mmfba73c71/1.0/icloud/1.0
And
Delete a contact on iCloud.com (eg: get rid of duplicates completely)
https://support.apple.com/en-au/guide/icloud/mm6704c88a/1.0/icloud/1.0
For more:
The iCloud User Guide online:
(Click on "Table of Contents" ... or use the "search" ... at the top of the page.)
https://support.apple.com/en-au/guide/icloud/welcome/1.0/icloud
If Difficulties ? : Apple support have a useful article online:
If you can’t create, import, edit or delete contacts on iCloud.com
https://support.apple.com/en-au/guide/icloud/mmc1cd5b86a1/1.0/icloud/1.0
Hope you hit on some combination of what's possible to tackle and "tame" your contacts.
Cheers :)