How do I get rid of Criteo cookies embedded on my Safari browser on my IMac?

Go to Safari > Preferences > Privacy then click Manage Website Data then type Criteo in the search field top right corner of the window then select the cookie(s) then click Remove > Done.

As the 2nd article points out, they are capable of regenerating after deletion with files that go to many parts of the system.

Safari/Browsers – can’t delete cookies

Evercookie

The myth of the dangerous cookie

Quit Safari.

In Finder go to Go menu and then Go to Folder.

Copy and paste this ~/Library/Safari/Databases.

Delete the contents of the folder.

Launch Safari again and check if all is ok.

If that doesn’t work, copy and paste this ~/Library/Safari/LocalStorage.

Delete the contents of the folder.

Then go to Safari/History and delete any entries for the related websites.

Test.