Products Duplicated After Import (Same Sku Different Id)

I found some products have been duplicated during import. I don't know how possible is that because all products has unique SKU (CODE). How can I remove duplicated products from database. It's really bad.

Any idea how to remove it? I have counted 1800 products duplicated.

You can use our addon to find duplicates

and delete products manually 250 per page.