President Obama left North Korea as a problem to be dealt with.  

He also sent an Armored  Brigade to Poland by way of Germany to threaten Putin's future ambitions in Eastern Europe arriving about on Inauguration Day which Trump also must acknowledge and deal with.

Obama had little to no choice on either of those unless he chose to act himself in either location which didn't happen in Syria (remember the 'line' he said not to cross?--it was crossed) or against the Russians or in North Korea during his administration.  A couple of Executive Orders about Russian oligarchs' finances or forbidding them entry to the US as aliens by Obama in the last days of his reign didn't accomplish much.

Should Trump bomb North Korea or Russia or both? Simultaneously or one before the other to convince the other that he is serious?