Sometimes the sync process is going wrong somewhere along the line and creating duplicate lists of some contacts. You have to take time to find and delete the duplicate contacts by hand. AddressBook Cleaner is exactly the utility you need to help you find all the contacts which match the predefined fields, and mark the ones to be removed. All you need to do is run the application and perform simple clicks.
AddressBook Cleaner supports English, Deutsch, Français, Italiano, Español, 日本語, 中文.