Fear of an American president is a good thing.
Many think the American hostages in Iran were released the day Reagan became president, precisely because the Iranians were afraid of what Reagan might do. And that line of thinking is that Iran had no fear of Jimmy Carter and his dealing with the hostage crisis.
“Upon this a question arises: whether it be better to be loved than feared or feared than loved? One should wish to be both, but, because it is difficult to unite them in one person, it is much safer to be feared than loved.”
Niccolo Macchiavelli
In the hostage situation, fear was a factor.
However, the key in negotiating with an adversary is to treat them with respect (no name calling, no finger pointing, no arrogant virtue signaling), then find out what they want, and see if you can give them some of it.
Reagan’s people cut a deal that was a win win.
Trump was also an expert at that type of negotiation.
It is the combination of real strength and willingness to pursue win win outcomes that makes a great negotiator.