Caren,

The least harm is that Trump would increase prices on almost everything Americans buy because of his tariff fixation.

But then the Biden Administration is about to impose tariffs on Chinese imports of value under $800 sent directly to American customers. This will affect consumers significantly, but they don't push back.

Trump would do the most harm in foreign policy by undermining alliances and international institutions that America built for world security, trade, health, etc. He would favor unilateral transactions rather than multilateral longer-term agreements.

Note, however, that Joe Biden has introduced zero new trade agreements and failed to reenter the Iranian nuclear agreement or the TPP.

Many thanks. Best.