Comprehensively, nothing can be shown to evidence any failure whatsoever either.
Of course neither of us can make any claims of what a second Trump admin would have accomplished...
But I think the general knowledge in the US that Beiging directs any offense by NK is very useful.
The objectives stated by the President, and his Secretary of State Pompeo, were not achieved or reached with the North Koreans. The Directorate of National Intelligence states they continue to be a major national security priority for the United States. You would have to tell me in fact what HAS been accomplished. Can you specify those? I am happy to provide the things they have not resolved.