Releasing all personal and business tax returns for the past 10 years may be enough. Journalists and voters can take it from there.
A dishonest person will be a tax cheat. Also, tax returns will reveal dangerous indebtedness (for example, how much money Trump owes to Russia).
If Americans could have seen Trump’s tax returns during the campaign, he never would have been elected president. He knew that — that’s why he never released them.