His policies (if they actually go through) will take the U.S. back 30 years all the way to the Reagan administration. He will undo everything Obama and Clinton have done, seriously, he wants to repeal Obamacare.
I hate it when people say both Hillary and Trump are equally as bad! NO, policy-wise, Hillary would have tried to progress or at least keep the status quo, Trump wants everything back to how it was when Reagan was in office. Hillary actually has experience running things, she would have made a competent leader, the only thing Trump is good at running is his mouth. Trump is the kind of leader I can see getting on the bad side of some other world leader on a personal level thus straining international tensions even more.
On a personal level, Hillary's okay, she's not frickin' Mother Teresa, but she's not terrible. Trump on the other hand openly disrespects women and minorities, the effin' KKK supported him, not that he acknowledged them, but that says a lot about how he comes across as a person to those who have never heard him speak.
I'm not anti-Republican, I would have been fine with any of their candidates in the primaries. Trump should never have been their nominee in the first place. I would have killed for a Bush, or McCain, or Romney, or even Palin to run in this election.
EDIT: He also wants to bring back coal mining/production/energy!!! COAL! Thanks, we're gonna end up like frickin' China. The Earth's gonna get back at us by releasing the vehement ire in the super volcano underneath Yellowstone...