What has he achieved?

After Donald Trump met Kim Jong Un, what has he achieved?

At first, Trump played down Kim Jong Un ‘rocket man’ because Kim shot many ballistic missiles from North Korean Peninsula to intimidate the neighboring countries including Japan and even U.S.
Eventually he changed his attitude toward him because Kim
promised to meet him.

For Donald Trump, meeting with Kim Jong Un has brought very
big impact on mid term election for U.S. president because
it was the first time that an incumbent U.S. president met with
a North Korean leader officially.

Their meeting was memorable, however there was not so much achievement from the meeting.