Best case scenario after a Trump win: He does all the good things he's proposed but doesn't do the bad things. Like... he surrounds himself with good people giving good advice after learning his lesson from his first term, is pro-growth, pro-peace, supportive of civil liberties, Elon gets through to him on basic math and Tulsi on basic history, etc. Ukraine is allowed to negotiate a settlement where they don't lose too terribly much and he uses the threat of withholding Israeli aid to pull Netanyahu back in a way Biden/Harris were unwilling to. The budget still don't look great, but there's at least a possibility of reigning in some military spending or getting the feds out of education or something.
The best case scenario after a Kamala win: The GOP controls Congress and nothing gets done.
Worst case scenario after a Trump win: He does the bad things he's proposed but doesn't do the good things. He surrounds himself with neocons and Fauci-style bureaucratic busybodies, institutes tariffs that cripple the economy, his shit talking gets us into a war rather than giving enemies pause and preventing war, and he puts teeth behind bluster of authoritarian impulses on issues not even limited to immigration. He not only doesn't at least pull us back to pre-COVID levels of spending, but lets the growth continue, and tries to insert himself into decisions on interest rates to avoid any necessary structural changes.
The worst case scenario after a Kamala win is Democrats controlling Congress and being active, packing the court, and in her role as Commander-In-Chief gets us into yet another war that spirals out of control.