There's a case for both Bush and Reagan but Trump is an incredibly unserious answer
Hear that, y'all? It's soo "incredibly unserious" to believe that Trump potentially enabled long-term damage with his favoring of damaging right-wing policies such as the gutting of regulations for big businesses, the cutting of taxes for corporations, doing nothing for the environment, etc., in addition to being the least qualified & least deserving of the office at the outset; completely disregarding precedent, procedure, & process & greatly weakening the office in doing so; unforgivably damaging this country's political discourse; royally mishandling a deadly pandemic to the tune of 559K lives lost & counting; & - oh yeah - inciting a literal f**king insurrection upon the U.S. Capitol on the way out.
You can argue that Reagan & W.'s presidencies did more damage, but choosing to merely engage in ad-hominems instead is what's "incredibly unserious" here.