Error: THE SERVER PRINCIPAL ALREADY EXISTS – MSG 15025, LEVEL 16, STATE 2, LINE 1

I cannot find the login physically though but getting the error while trying to create a new login. 

Use below scripts to fix the issue

 select suser_sid ('Domain\loginName');

go

Result: 0x0105000000000005150000000C04XXXXXXXXXXXXXXXXXXXXXXXXX

select * from sys.server_principals sp

where sid=0x0105000000000005150000000C04XXXXXXXXXXXXXXXXXXXXXXXXX

IF  EXISTS (SELECT * FROM sys.server_principals WHERE name = N'Domain\LoginName')

    DROP LOGIN [Domain\LoginName]

Able to create a new login now.