Early in his career, Trump apprenticed himself to Roy Cohn, an unprincipled lawyer who taught the young Trump how to gain wealth and influence through ruthless bullying, profane braggadocio, opportunistic bigotry, baseless lawsuits, lying, and more lying. Yet as Trump’s “fixer” with politicians, judges and mob bosses, Cohn remained utterly loyal to Trump and his father, Fred.
Source: wiktionary