Ahead of his first Group of 20 summit, U.S. President Donald Trump took to Twitter to weigh in on his concerns.

From bad trade deals ("the worst") to North Korea's nuclear ambitions ("this nonsense") to steel dumping ("don't like"), Trump highlighted what he had hit head-on in Hamburg.

The problem for the president is that he comes home from the Group of 20 summit with little concrete progress on those issues, while the differences between himself and the rest of the world are greater than ever.