For President-elect Trump to end the war, the administration running the country at that time would have to appoint him Special Envoy to Ukraine and Russia. This might involve the UN or NATO, but probably not.
So who would be running the government at that time?
Biden? He would never appoint Trump to that kind of position unless failing to do so would quickly set off global thermonuclear war.
Harris? The same.
Speaker Johnson as Acting President due to Biden and Harris being out of office for some reason? Possibly.
A miliary government in charge due to circumstances resembling civil war or the nuclear decapitation of DC? Possibly.
This requires some more analysis.
Indeed....