1985: NYC sues Trump for harassing tenants
New York City sued Trump in 1985, accusing him of systematically harassing tenants in one of his buildings. New York state officials also opened an administrative action relating to Trump's poor treatment of his tenants. 
1984: Trump sues critic for libel
In 1984, Trump filed a $500 million libel lawsuit against Paul Gapp and the Chicago Tribune for criticizing a proposed skyscraper.  Trump's lawsuit was dismissed by a judge who ruled that the First Amendment protects statements of opinion.
1983: Judge rules Trump harassed tenants
A judge ruled in 1983 that Donald Trump had harassed a tenant at Central Park South in an effort to drive the man out of his building. 
1982: Trump Management Racial Discrimination Case
Trump Management, the business managing the Trump family's rental properties in New York City, was sued for racial discrimination in 1982. The company reached an out-of-court settlement that provided one out of four available rental units would be provided to minorities. 
1981: Trump Tower Tax Abatement CaseTrump sued New York City in July of 1981, demanding the City grant a tax abatement to Trump Tower.  The lawsuit ultimately reached New York's highest court, which ruled that NYC officials had improperly denied Trump the abatement.
“Donald Trump, the developer, is in the newspapers almost every day for one thing or another. [...] Both the city and the state, in detailed papers, have brought actions against him for mistreatment of tenants - the state in an administrative proceeding and the city in a lawsuit seeking heavy fines. (New York Times, Sydney Schanberg column, March 9, 1985)”“Donald Trump, the developer, clearly thinks architecture critics are the most powerful people in the building business. There can be no other explanation for the $500-million libel suit he has just filed against the architecture critic of The Chicago Tribune, Paul Gapp, and the Tribune Company, taking issue with a column Mr. Gapp wrote in mid-August questioning Mr. Trump's proposal to build the world's tallest building, a 150-story skyscraper off the southern tip of Manhattan.”“In his recent decision, Judge Weinfeld emphasized that the First Amendment protects expressions of opinion, “however unreasonable or vituperative since they cannot be subjected to the test of truth or falsity.” [...] Paul Gapp and the Chicago Tribune did not, said Judge Weinfeld, cross that line. [...] Judge Weinfeld dismissed Donald Trump's complaint. (Washington Post, October 19, 1985)”“A judge said yesterday that Donald Trump, the New York real-estate developer, had tried to “harass” a tenant into moving out of a Central Park South building Mr. Trump owns.”“Three real-estate brokers and nine landlords agreed yesterday to offer to blacks one out of every four vacant apartments in three predominantly white Queens neighborhoods. The agreement was part of a settlement, reached in Federal District Court in Brooklyn, of three class action suits filed in 1982 by the Open Housing Center of New York and by nine black prospective tenants. The suits charged that the defendants were responsible for a pattern of discrimination against members of minority groups seeking apartments. [...] The landlords are [...] and Trump Management. The president of Trump Management is Fred Trump, father of the real-estate developer Donald Trump. (New York Times, October 25, 1984)”“Donald J. Trump, the real-estate developer, filed suit yesterday against New York City and a city housing official for $138 million, charging that they discriminated against him by denying a tax abatement for a major building he is constructing. (New York Times, July 23, 1981)”“The state's highest court ruled unanimously yesterday that New York City had improperly denied a multimillion-dollar tax abatement to Donald J. Trump. (New York Times, December 15, 1982)”