Some tax laws are worse than others. The 1986 Tax Reform Act is generally considered one of the best. The 2017 Tax Cuts and Jobs Act is generally considered one of the worst, although I would say it is too early to tell what its long-term impact might be, and some of its worst features (like the Code Sec. 199A deduction) might be repealed in the future.
Another example of a generally condemned tax law is the American Jobs Creation Act of 2004. This law was a must-pass piece of legislation because Congress needed to react to the sanctions imposed upon the United States by the EU as the result of its victory in the ETI litigation at the WTO. The AJCA included such beauties as a temporary participation exemption that did not create any jobs, a significant increase in the potential for cross-crediting in the foreign tax credit, a manufacturing deduction that extended to software and film production, and a deeply flawed anti-inversion rule that immediately gave rise to a second wave of inversions.
But these bad features were not particularly lasting. The participation exemption only lasted one year, the cross-crediting provisions were significantly revised in 2017, the manufacturing deduction was repealed in 2017, and the anti-inversion provision became less relevant after 2017. Any damage that was done was temporary.
To get to a bad tax law whose effects were really long-lasting, one should go much farther back to the Revenue Act of 1918. This law was the last major tax law of the Wilson administration, but despite its name was only enacted in 1919 and therefore was the first post-war tax law. During WW1 the income tax had grown from a largely symbolic measure with rates in the single digits to the major revenue source of the Federal government, with a top individual tax rate of 77%. The Revenue Act of 1918 maintained the high rate for 1918 but reduced it for 1919 and 1920. This reduction was the work of the GOP-controlled Senate and reflected the desire to return to “normalcy” after the war ended.
Avi-Yonah, Reuven S. "The Worst Tax Law Ever Enacted?" International Tax Journal 47, no. 1 (2021).