Manual data validation in Excel

I have an excel file of contacts that are duplicate records with slightly different data (records created at different points in time). I need this manually reviewed for each contact, data corrected in the record that is closest to current correct data, and the outdated record marked to be deleted (NOT deleted, just marked).

Linkedin would be the primary source for correct data.

There's about 800 or so records so the result would be about 400 correct and non-duplicate records.

A small sample is attached for you to see the file.