Russian invasion of Ukraine
Failing to support Ukraine against the Russian invasion
Ukraine's city of Avdiivka was completely lost to Russian invaders directly because of Trump
and his forcing the Republican party to vote against a critical aid package for Ukraine.
The months-long delay in passing the aid package caused the loss of the city.
Handling of the Pandemic and COVID deaths
The USA lost about 1 million lives to COVID.
It may be that up to half of those deaths could have been prevented if not for Trump's politicization of the pandemic and the response to it.