Glenn E. Meyer said:
Mustafa Ashu
Shot the King of Jordan in 1951. Said king was likely to make peace with Israel... fear of assassination in 1967 led King Hussein to join Nasser in the 6 Day war.
To be fair, Ashu was accused by the Jordanian government of having been part of a larger plot, and several alleged co-conspirators were arrested, convicted, and executed.
However, IIRC some historians consider this to have been a dog-and-pony show intended to scapegoat some irksome political dissidents while distracting the citizenry from the government's failure to protect their king at one of the holiest sites in Islam (he was killed on the steps of the Al-Aqsa Mosque in Jerusalem). Since Ashu was killed by the king's bodyguards at the scene, the truth will probably never be known.
One key fact about this assassination is that Hussein, then 15 years old, was standing next to his grandfather King Abdullah I at the time and was also shot by Ashu, but the bullet was deflected by a medal he was wearing over his heart, most likely saving his life.
This is generally seen as a major factor leading to Hussein's fear of assassination and his wariness of being perceived as an Israeli sycophant.
IMHO another good nominee is
Yigal Amir, the Israeli student who shot and killed Israeli PM Yitzhak Rabin in 1995.
Despite being on opposing sides, Amir and Ashu have several interesting things in common:
- Both are seen by many as having been lone actors, conspiracy theories notwithstanding;
- Both were alleged to be right-wing hardliners seeking to prevent Israeli-Jordanian peace;
- Both are thought to have substantially set back the Israeli-Palestinian peace process.