My biggest concern if Trump is ever inaugurated

I would say if Trump is actually inaugurated president at the end of January I fully expect within the first year that North Korea is going to piss him off to the point where he nukes Pyonyang, North Korea off the map one night while everyone is asleep there.

Do I really believe this?

Yes.

Will he ask China before he does this?

No.

However, what is really strange about this is China might be actually grateful to be rid of Kim Jong Un. So, it might be in China's strategic advantage to rule North Korea themselves for awhile so so many people aren't starving to death there. This is likely what could happen once the North Korean Army is pacified by China.

Another reason this is likely to happen is the Obama Administration now considers North Korea as the biggest threat presently to South Korea, Japan and the United States. The reasons for this is North Korea has developed not only nuclear weapons but has also developed the capacity to hit Seoul or Tokyo with a nuclear weapon on a missile. So, because North Korea is so insane expect them to be blown off the map sometime in the first year Trump is elected whenever they piss him off enough one night.

Is this a good or bad thing?

It is likely good for the U.S. and for China as long as China steps in an rules North Korea after this happens. But, if South Korea or Japan is invaded or nuked by North Korea all bets are off. This could just start a world war for various reasons.