Conversation so far:
What happened with Ben Carson on 2016?
On March 11, 2016, a week after Ben Carson ended his presidential campaign, he endorsed Trump, calling him part of the voice of the people to be heard.
What else did Ben Carson say about Donald Trump besides calling him part of the voice of the people to be heard?
At the press conference, Ben Carson said Donald Trump had a cerebral side
What did Ben Carson say about Donald Trump that drew criticism?
Ben Carson's subsequent comments that Americans would have to sustain Trump for only four years if he was not a good president drew criticism

Question: what was his greatest accomplishment?
Self-contained rewrite: What was Ben Carson's greatest accomplishment?