My problem with multiplication of contacts began about two weeks ago when I enabled Contact sync in Link to Windows. I already had my Outlook contacts synching with the Contacts app on my Samsung phone for a long time and it was working fine. I have now uninstalled Link to Windows from my phone and manually unmerged all contacts on my phone and deleted the duplicates. I was left with the orphan contacts on Outlook on the web, even after I deleted them from the Windows Outlook app. However, I just noticed that the orphaned contacts have now disappeared from the web version of Outlook.
I am not game to reinstall Link to Windows on my phone, but I can live without it.
An observation: All of the duplicated contacts appeared to be ones with only a first name or a last name, not both first and last name, or they were merged on the phone with a contact that had only first or last name. Perhaps there is a bug in how Outlook compares contact names with existing contacts when synching?