How can I stop my iCloud contacts from duplicating?

I know this topic has been beaten to death over the years but I can't seem to find a solution. after syncing my contacts via iCloud selective but numerous duplicates keep appearing. I've gone through multiple times to attempt to "merge duplicates". I have turned off all other sources except iCloud but nothing seems to help. They merge and then begin to repopulate. Again apologies if this is a dead horse but I'm not seeing any real solutions anywhere.

[Re-Titled by Moderator]

Original Title: Massive duplication of contacts