The largest issue concerning trump's taxes is not any illegal deductions he may have claimed while filing. No.
The largest issue is that his tax returns would reveal details about his dealings with Russia, Saudi Arabia, (and perhaps China). His tax returns would reveal the true extant of his business empire (which is currently only guessed at) . it would reveal much about his debt levels, and which countries and banks hold that debt. We could find out if he is favoring governments and leaders in order to further his own personal business dealings, speed projects, and forgive his debt. We would learn if he actually has assets to equal the net worth he has claimed to his supporters, which is strongly doubted by those in the financial community.
trump's taxes could teach us a lot about his financial interests and shed light on any legislation he proposes or any sanctions he imposes (or lifts) or any WAR that he starts in order to line his immoral pockets.
Every candidate for President in the US has released their tax returns for the last half century... trump has falsely claimed that he can't release his because they are being audited. That's a double falsehood, since the IRS does not forbid disclosure of returns that are being audited, and there is ample evidence that no audit is taking place despite trump's lies.
trump's lies are in a brand new category, different from any run-of-the-mill lies our politicians have told in the past. This person has taken office in order to line his pockets, not to serve the American people. There is suspicion that he may be suffering the first stages of Alzheimer's disease like his father before him, which may explain why he uses his children to buffer for him in every situation he can. He embarrassingly claims high intelligence to the press (as though truly intelligent people would need to advertise that fact). He has a third-grade command of the English language. He does not appear to understand the US Constitution which he has been sworn to protect and defend. he doesn't even understand that our government is divided into three EQUAL branched (legislative, executive, and judicial). He has repeatedly expressed astonishment and resentment that the courts are able to block his executive orders because they are un-Constitutional.
He has chosen his official Cabinet by their appearance, as though he was casting a reality TV show. He took no interest in their qualifications (or lack of qualifications).
He repeatedly abandons prepared statements to tell anyone who will listen that he won the Electoral College by a record-setting landslide (false), and that he certainly would have won the popular vote if MILLIONS of illegal immigrants hadn't voted for his opponent (ales demonstrably false). After meeting with former President Obama during the transition, he expressed dismayed surprise that he would have to work so hard... he actually didn't realize that before he won the election.
He repeatedly praises Vladimir Putin and forgives Putin his murders and illegal wars, because he said that Putin likes him and he's won't insult someone who likes hi, There is evidence from US intelligence operatives that A) He and his staff communicated with Russian intelligence operatives during his campaign and B )Putin has possession of compromising video and audio of trump with Russian prostitutes in Moscow, committing perverted sexual acts at trump's behest, and these tapes are being used to blackmail trump into treating Russia favorably.
trump didn't know what the Geneva Convention is, Angela Merckel had to explain it to him.
trump wants to re-institute torture of prisoners, and wants to order the military to murder wives and children of terrorists.
He ran on the idea that he would run America like a business, and no-one realized that his 6 bankruptcies and repeated failure to pay contractors and other debtors is his idea of how to run America.
He wants to lower taxes for the billionaire class and cut benefits for senior citizens and poor people and minorities.
trump wants to dissolve NATO and hints that he may not fulfill our obligation to defend fellow member nations according to the treaty.
He wants to start a war in Iran, and possibly attack Iraq again, He has stated on multiple occasions that he wishes to steal the oil fields from various Middle-Eastern countries that America invades, even though it has been explained to him that this is a war crime called "pillage". He doesn't care, he wants to steal the oil.
trump insulted and hung up on your own PM, and he has unnecessarily antagonized other world leaders.
American intelligence agencies have leaked to the press that they are withholding sensitive information from trump, because they believe that trump will forward this information to Putin in Russia. "The Kremlin has ears in the Situation Room", said one high-ranking operative. This, for any other citizen, would be called Treason and Espionage and Giving Aid and Comfort to the Enemy. For Traitor trump it's just a typical day.
And, of course, there's the stupid, stupid, stupid Wall he wants to build, that will cost American taxpayers billions, cause enmity between the US and Mexico, and do less than nothing to stop undocumented immigration.
There are so many other bad things about trump, so astonishingly many bad things, that it would be impossible to list them all in a forum post. The guy is a walking disaster. This is a man who could order a nuclear strike on any country on earth with the same peeved abandon that he shoots out his idiotic Tweets. trump might kill us ALL just because his over-inflated vanity is wounded.
He is not intelligent, he is not learned. He is not stable, he is not predictable. He is not wise, he is not humble,. He is not a good man. He is weak, he is a fool, he is dishonest, he is degenerate, he is warlike, he is narcissistic and authoritarian, he displays mental confusion, and he may be either mentally ill or suffering from degenerative Alzheimer's disease.
This administration is the most alarming disaster that America has ever faced, and I fervently hope we can survive this administration as a Constitutional Democratic Republic, without descending into tyranny, autocracy, plutocracy, kleptocracy, idiocy.
So, yeah. You might say that trump is "different".