An ex-Marine "went into combat mode" against a crazed vandal and beat him senseless when he was attacked at the fancy Upper East Side apartment building where he works as a doorman. Andy Frederick, 48, was working the overnight shift in the lobby of the building at 44 East 67th St. around 1:50 a.m. on Friday, when he saw Betzelel Levin, 29, walking by and then heard glass shattering, sources said. Frederick dashed outside and approached Levin, who allegedly had busted one of the building's windows and was about to kick in another. "The guy struck [Andy] in the chest....