"Hillary was openly hostile with Russia, and while I doubt it would have reached the point of increased risk of nuclear war, Russia still has real nukes, so you never know. Trump on the other hand is, if anything, too friendly with Russia."
Consider very recent history. George W. Bush ran his whole campaign in 2000 on a "compassionate conservative" platform, including that we needed to put America first, not being involved in foreign adventures, stop telling other countries what to do, etc. But he was a dimwitted cowboy wannabe who had no capacity for a real commitment or follow-through to that. He surrounded himself with belligerent neocons like Cheney and Rumsfeld and gave them incredible power. He spent the summer of 2001 saber-rattling at China which turned out not to be the actual brewing threat. Then we did suffer an actual attack on 9/11 and bam, within 24 hours he's freaked out and flipped to the exact opposite; global alliances, regime change, and a philosophy of first-strike invasions if needed around the globe. Before his term was done he'd started two separate intercontinental wars -- one having entirely nothing to do with the attack on us -- which have proved to be the longest in American history, and still not done after almost two decades now.
That is the proven historical result of a fundamentally dumb, belligerent, yahoo, volatile commander-in-chief. It's easy to predict; this is the standard reaction of a chaotic, short-attention-span bully. Sometime in a quiet space ask yourself this: Is Trump truly more or less volatile than George W. Bush?