Trump's sycophancy with Kim Jong Un might lead in the future to security issues and increased tensions in the Middle East - in Iran.
There's an interview in "Der Spiegel" with Foad Izadi, a lecturer for North American studies at the University of Teheran, whom himself studied in America. (Keep in mind the following is a summary of the interview, so not my words, thank you).
Izadi argues, that the treatment of North Korea by the Americans caused deep resentments in Iran at last. The reason why is that there have been a lot of concessions towards North Korea to support their economy, if they are willing to abandon their nuclear weapons program, before they even started negotiating at all. Iran on the other hand in the past had to meet a lot of conditions, before America was even willing to sit at the same table.
He argues that it was promised to Iran, that they can start selling their oil again if they are stopping the weapons program - so they stopped it, and nothing happened. On paper it was lifted, but In realit this is impossible, because due to the American sanctions no bank is going to make the necessary money transactions. So Iran feels mistreated and wounded.
This lead to a darkening of the mood in the country. Many Iranians are now more then ever convinced that they cannot trust the West, America and Europeans alike.
So in short he fears that at the next presidential election the people are quite likely going to elect a hardliner as president again, because in the end all of this plays into the hands of the extremists. When Ahmadinedschad was elected, he had a few hundred of centrifugues; at the end of his presidency there were 19000. Therefore many are more convinced than ever that in order to be treated with respectfulness by the West, you've first got to have a far progressed nuclear weapons program, as North Korea clearly showcases.
So to sum it up Trump's obsession with dictators might lead to getting a real hardliner as next Iranian president, to a renaissance of the Iranian nuclear weapons program in the end, and therefore a heavy destabilization of the whole region, because Iran is more than ever convinced that you've got to have a nuclear bomb first, before you are getting treated seriously by the Americans&rest of the Western world.