How to merge 20,000 duplicate contacts on iPhone and iCloud?

I'm on an iPhone 16 pro max and have multiple duplicate contacts (nearly 20,000. Sadly, I'm not that popular)which are also in my iCloud account.

I have searched for how to merge them but, the 'Duplicates Found' that should appear below My Card is not there.

Any ideas?

[Re-Titled by Moderator]

Original Title: Duplicate merge