In inflation-adjusted dollars, Trump's tax bill is the fourth-largest since 1940. And as a percentage of GDP, it ranks eighth.
By taking into account the percentage loss to the GDP as a direct result of the tax cuts, President Ronald Reagan's tax cuts accounted for 2.9% of the U.S. economy in 1981 while the same stands at 1.1% under President Trump's tax reforms. Moreover, according to the Committee for a Responsible Federal Budget, Trump's tax cut would even fall behind Obama's tax cuts when measured by inflation-adjusted dollars. This indicates that there have been other tax cuts reforms that were better than Donald Trump's tax cuts from 2017.
There have also been massive tax cuts under President Coolidge, President Harding, and even President Kennedy in the 1900s. Another thing to keep in mind is that the predecessors of the Presidents mentioned above were forced to heavily increase the taxes resulting from the great depression after the two World Wars. Coolidge, Harding, and Kennedy had to heavily cut taxes to stimulate the economy and increase people's spending power. Notably, none of these presidents had given corporate tax cuts. Still, they had increased the taxes for corporate companies while considerably reducing the overall federal taxes in the United States. But, Trump's tax cuts were mainly focused on corporate tax cuts.
But, when measured about the cut to the overall GDP, Trump's tax cut was not the largest in history, was implied. Thus, we can conclude that President Trump's tax cut and reforms are not the largest in U.S history. The GOP plan comes in eighth or fourth place, as measured by a percentage of gross domestic product or inflation-adjusted dollars.