Transcript for The Year 2018: Trump on the world stage

The year began with north Korean leader Kim Jong-un and president trump exchanging threats. But this time, the dictator trump once called "Little rocket man" also opened a door to diplomacy. Eventually leading all the way to that historic Singapore summit. He reaffirmed his unwavering commitment to complete denuclearization. Since then, there have been no further missile or nuclear tests. And a north Korean parade we saw skipped the usual array of weaponry. There is no doubt, Kim Jong-un has arrived. Still, to date, there have not been any verifiable steps towards the ultimate goal of denuclearization. But the president appeared to move on. I would like to congratulate you -- To another authoritarian leader. We had a direct, open, deeply productive dialogue. Standing beside Vladimir Putin in Helsinki, the president seemed unconcerned with criticism that he was far too friendly with the man who has denied the CIA's assertion his country interfered with U.S. Elections. President Putin was extremely strong and powerful in his denial today. The president has a completely different approach to diplomacy. He certainly has a way of getting along with dictators. The drama on the world stage would only intensify. This time, with a brutal murder. Despite growing evidence from his own CIA that Saudi Arabia's powerful crown prince Mohammed bin Salman orchestrated the killing of journalist Jamal khashoggi, president trump seemed unconvinced. Maybe he did, maybe he didn't. And in Syria, while later the white house would announce the pullout of troops, evidence of a chemical attack, brought a counterattack by the U.S. The purpose of our actions tonight is to establish a strong deterrent against the production, spread, and use of chemical weapons. And around the globe, relationships with allies were tested this year. We are finally putting America first. That didn't just mean stepping in front of the queen in an apparent awkward breach of protocol. But trump especially taking aim at the leaders of the uk, Canada, and France, among others. Germany, as far as I'm concerned, is captive to Russia. A bull in a China shop, is probably the best way to sum up his diplomatic style. He doesn't relish disruption, he lives on disruption. That disruptive style did result in a new trade agreement with Mexico and Canada, but also prompted protests and belittlingof trump worldwide. My administration has accomplished more than almost any administration in the history of our country. And when many seemed to laugh at him at the united nations -- Didn't expect that reaction, but that's okay. Trump later claimed -- They weren't laughing at me. They were laughing with me. We had fun. Fun or not, trump's brash style is sure to continue in 2019. It's a meat-ax type of approach to foreign policy, but why would we expect it to be any different than that? That's who he's been.

This transcript has been automatically generated and may not be 100% accurate.