This is a listing of some of the law suits to which Trump has been a party over the years, but it does not include just threatened litigation:
US Department of Justice, Racial Discrimination in Housing. In 1973 Trump Management Corporation was sued by the Justice Department for racial discrimination by not renting to blacks. Trump sued the Justice Department for $100 million for defamation but the defamation suit was dismissed. Trump settled the law suit but was Trump Management was later again charged with continuing to discriminate against blacks.
Stock Analyst Suit Against Trump for Defamation and Contract Interference. In 1989 Marvin Roffman was a stock analyst who accurately predicted that Trump's Taj Mahal would fail after it opened. Trump was incensed and brought pressure on Roffman's employer to fire him. Roffman won an aribitration with his employer and sued Trump. The suit was settled under terms that prevent Roffman from discussing them.
Estimating Trump Wealth. When Timothy O'Brien, author of TrumpNation, The Art of Being the Donald, wrote that Trump's wealth was between $150 and $250 million, Trump sued O'Brien and the publisher for $5 billion in damages in the Camden, NJ family court. Trump fought releasing complete tax returns and the court decided against Trump, and the decision was confirmed on appeal.
Prospective Building Size. In 1984, Trump sued the Chicago Tribune for $500 million after the publication’s architecture critic, Paul Gapp, wrote an item suggesting Chicago’s Sears Tower, then the world’s tallest building, would remain as such, despite Trump’s plan to build a taller structure in downtown Manhattan
Four Bankruptcies. Trump companies have filed Chapter 11 bankruptcies four times, in 1991 over the Taj Mahal (Marvin Roffman was proven correct), 1992, 2004, and 2009. Although the bankruptcies were for corporations and were not personal bankruptcies, Trump had some personal guarantees and ended up losing his yacht and an airline among other things. An estimated 5% of the biggest 500 companies have filed for bankruptcies in the past two decades.
US Securities and Exchange Commision, Misleading Investors. The SEC sued Trump Hotels & Casino Resorts, Inc. alleging that it mislead investors by including one-time gain as operating results in its third quarter 1999 results. The suit settled after three years.
Trump Towers Litigation. Undocumented Polish workers were used for demolition leading to building of Trump Towers. The workers were paid sub-union wages and many ended up not being paid when subcontractor had financial problems. Workers sued Trump alleging conspiracy to avoid paying union benefits. Suit languished for years eventually settling.
Trump "University" Fraud Suit. NY Attorney General Fraud Action Regarding Trump University. In 2013, NY Attorney General filed a $40 million dollar law suit against Trump for essentially defrauding students who enrolled in his "university." In 2010 Trump dropped the word "University" after receiving a letter from the New York Department of Education accusing him of misleading the public by running an unauthorized school. In a separate action, Trump filed an ethics complaint against the attorney general.
Trump "University" Class Action Case. Art Cohen, a former Trump University student also filed a class action against Trump in California.
Beauty Queen Law Suit. Sheena Monnin was Miss Pennsylvania when she entered Miss USA, a Trump pagaent. She resigned her title in 2012 after failing to make the top 16 in the national pagaent, claiming that the contest was rigged. Trump sued her, taking a $5 million dollar award. She later sued her attorney for malpractice and apparently used the proceeds from that case to settle the Trump litigation. Michael Cohen, long-time Trump attorney subsequently bragged that he had ruined the contestant's life.
(1) Valerie Strauss, "Trump University: Why the N.Y. attorney general called it a scam," Washington Post, Aug. 8, 2015,https://www.washingtonpost.com/news/answer-sheet/wp/2015/08/08/trump-university-why-the-n-y-attorney-general-called-it-a-scam/
(2) Marcus Baram, "Donald Trump Was Once Sued by Justice Department for Not Renting to Blacks," Huffington Post, June 29, 2011, http://www.huffingtonpost.com/2011/04/29/donald-trump-blacks-lawsuit_n_855553.html
(3) Christina Binkley and Judith Burns, "SEC Brings CAse Against Trump Hotels Alleging Improper Use of "Pro Forma," Wall Street Journal, Jan. 17, 2002, http://www.wsj.com/articles/SB101119802590296360
(4) Jonathan R. Laing, "Donald Trump's Blustery 1990 Campaign Against a Wall Street Stock Analyst," Barron's, Oct. 10, 2015, http://www.barrons.com/articles/donald-trumps-1990-campaign-against-a-securities-analyst-1444451156
(5) Ian Tuttle, "The Litigious - and Bullying - Mr. Trump," National Review, February 19, 2016, http://www.nationalreview.com/article/431575/donald-trump-tim-obrien-courtroom-story
(6) Olivia Nuzzi, "Haters Gonaa hate, Trump's Gonna Sue, Donald Trump Sued Everyone but His Hairdresser," Daily Beast, July 6, 2015, http://www.thedailybeast.com/articles/2015/07/06/trump-sued-everyone-but-his-hairdresser.html
(7) Brandy Zadrozny, "Trump Lawer Bragged: I 'Destroyed' a Beauty Queen's Life," The Daily Beast, July 31, 2015, http://www.thedailybeast.com/articles/2015/07/31/trump-lawyer-bragged-i-destroyed-a-beauty-queen-s-life.html
(8) Drew Harwell and Jacob Bogage, "What Trump didn't say about his four big business bankruptcies," Washington Post, August 7, 2015, https://www.washingtonpost.com/business/economy/what-trump-didnt-say-about-his-four-big-business-bankruptcies/2015/08/07/bc054e64-3d12-11e5-9c2d-ed991d848c48_story.html
(9) Constance L. Hays, "Judge Says Trump Tower Builders Cheated Union on Pension Funds," New York Times, April 27, 1991, http://www.nytimes.com/1991/04/27/nyregion/judge-says-trump-tower-builders-cheated-union-on-pension-funds.html
(10) Tom Robbins, "Deal Sealed in Trump Tower Suit, NY Daily News, March 8, 1999, http://www.nydailynews.com/archives/news/deal-sealed-trump-tower-suit-article-1.834028 (Terms of settelement of Trump Towers case sealed)