ContactClean has the lightest interface in this list, which is not very good but good enough to do the work for you. This app can delete duplicate contacts on your iPhone or iPad but only the contacts with similar names is free, you will have to do in-app purchases to merge or delete contacts with same phone numbers or email.
The interface is so light that you can merge contacts quickly without you having to go through different options. You can cleanup contacts automatically or detect duplicate contacts and merge or delete them yourself. You can even backup all of your contacts and email them to yourself through ContactClean. If you really want a very easy interface, do give ContactClean a try.
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