If Trump is elected, he intends to use the police, the National Guard, and probably the US Army to round up and "deport" every undocumented person in the United States - somewhere between 10 and 20 million people, by most estimates.
There's no indication that he intends to "exterminate" all these people. However, he's clearly indifferent to what harm may befall them, as they're rounded up, herded into concentration camps (excuse me, "detention centers"), and summarily shipped off... somewhere (likely not where they're from). Probably tens of thousands of US citizens will be wrongly caught up in this "program." People will die - from violence being detained, from terrible conditions in the concentration camps, from hostile governments wherever they're dumped.
Does Trump intend these deaths? Possibly not. Does he care? Who are we kidding; of course he doesn't care.
These actions will gut the US economy, and destroy whatever moral standing the United States retains in the world. If this is enacted (and Trump absolutely intends to do this), this will be the largest such purge of human beings since... yes... Hitler's "final solution" against the Jews, and Stalin's purges in the Soviet Union.
Most of us don't want the United States of America to be in that company, thank you. Most of us have concluded that Trump is more like Hitler and Stalin than he is "different" from them. Not the same - less calculating, more demented - but all in all, more similar than different.