Through you reinstalled this is the safest method to remove kubuntu desktop package:
sudo apt-get install aptitude ubuntu-minimal
sudo aptitude remove '?and(?reverse-depends(kubuntu)),?not(?reverse-depends(?exact-name(ubuntu-minimal))))'
This will leave your system with the minimal installation of Ubuntu, enough to boot, without Kubuntu packages.
Explaining what aptitude does:
?and(conditional1, conditional2): search for all packages that fulfill both conditions.
?reverse-depends(package): search for all packages which reverse dependencies include the package
?not(package): search for packages that doesn't fulfill this condition.
?exact-name(package): when using
?name() it search for any package that contains the name, for example it will find
?exact-name it specifies that it should be the exact name, is the equivalent to
^package$ regular expression.
If we were to interpret it in plain english: aptitude,
remove any package that has reverse dependencies with a package that includes in it's name
kubuntu, but that isn't reverse dependency of a package with the exact name of