In movies, a common trope is for the bad guy to kidnap a leading nuclear physicist to build them a bomb or something. Is this rooted in reality? Has a top scientist been coerced into this sort of thing before?
It's not common, to be sure, but it has happened, yes. Werner Heisenberg was targeted for potential assassination during World War II — the agent (Moe Berg, Red Sox catcher and general man of many trades) took a gun with him to a talk, and was going to shoot him if it seemed like the Germans though they would have an atomic bomb soon.
The Israelis have targeted many scientists. Iranian nuclear physicists, for one. The South African artillery maker Gerald Bull, for another.
There were fears in the Cold War that US scientists might be kidnapped while on conferences in eastern countries. There were instances of German scientists going to the USSR after WWII (for money) and finding themselves in a "gilded cage," allowed to work on weapons projects but not allowed any further freedom.