Export from a CRM, a webshop or a form and you get the same record twice — sometimes three times, with a different timestamp. Paste the file here, choose what makes two rows "the same", and keep one of them.
"Duplicate" is not one thing. Two rows can be identical everywhere (a real double export), or identical in the e-mail address with a different update date (the same person, exported twice). The first case is a whole-row duplicate; the second needs you to name the column that identifies the record. Picking "keep the last" is how you end up with the most recent version of each person.
For whitespace, empty rows, header normalisation and whole-row de-duplication in one pass, use the general CSV cleaner.