Dogberry on "Suspicious 'Administrator'"

The last freelance developer I hired to do a small job on my site (http://beyond-freedom.com) did something very fishy. I have been advised to uninstall and reinstall WordPress. I’m traveling abroad and plan to do just that when I’m back to the U.S. July 6th. Meanwhile, can someone advise me about how I can get rid of a suspicious User entry, listed as a second Administrator besides me. The entry is listed on Users’ page as follows:

Under Username, I see Username; under Name there’s Name; and under Role is listed Role.

Thanks,

Tafader