Hello, Is South Carolina unemployment compensation taxable? Should I have to add back the federal unemployment compensation exclusion on SC return? Thanks

Yes it is taxable. See Unemployment Tax Information | SC

You do not do any adding or subtracting with your unemployment.   All you need to do is enter your 1099G for unemployment and let the software take care of the calculations.   The software is up to date for unemployment and will treat the unemployment correctly on your federal and state returns.   

Enter your 1099G in Federal>Wages & Income>Unemployment

Go through the screens very carefully, making sure  to enter any federal/state tax you had withheld from the unemployment.