President Reagan's philosophy when it came to dealing with America's enemies was "Peace through strength."
That's a good philosophy to have, I think.
Except it led to the support of genocide in Guatemala.
Reagan was really pretty bad at foreign affairs, very inhumane, often downright illegal, and started off fairly poorly at being able to manage the Soviet Union.
Aside from direct support for death squads in Latin America, and the support of the genocide against the Mayans in Guatemala, we also directly funded a devastating civil war in Angola, fomented instability in the DR Congo, pretty much stood alone in recognizing and supporting apartheid in South Africa, acted rashly and with little understanding in Lebanon, lost the momentum of Camp David by ignoring the entire thing, botched the handling of Gaddafi, brought the US recklessly close to conflict with the Soviet Union (until he reversed course), and was generally fairly sloppy in his foreign affairs dealings. I might not rank him as bad as Nixon and Kissinger, but he engaged in a lot of immoral diplomacy that Clinton, George W. Bush, Obama and perhaps even HW Bush couldn't have even dreamed of getting away with (though Bush W. tried).
He had zero foreign policy experience going into the presidency but simultaneously had very strong feelings concerning it and the result was fairly disastrous for global stability at first. It was only really after he got caught with the Iran-Contra scandal that he got his ducks in a row foreign policy wise (so for most of his presidency he was largely inept).
One of his largest foreign policy successes was in Afghanistan and that move left the Taliban in power via his "whatever we need to do to win" strategy.