I’d say Bush, if we’re talking about things from a historical perspective.
If he never used his presidential powers to create a constitutional crisis, where he was allowed to not only start a war but remove himself from ever being persecuted or tried. Add in the fact that a huge amount of infrastructure, education, and healthcare investment suddenly became “defense budget.” He also spearheaded the CIA, DARPA, Pentagon; etc to create a national spying infrastructure on its own citizens that continues to this day and has embezzled over a trillion dollars. Add in the expansion and subsidization of the oil industry, which pushed us completely past the point of no-return in regards to climate change.
We literally would have not had Trump, if it weren’t for what Bush did. He’s just a symptom of the problem. Trump, apart from his incredible incompetence, did not actually do any real structural damage apart from stacking the federal courts.