Who was Haj Mohammed Effendi Amin el Husseini?
In the war he brought the Islamist forces (which were the nucleus of the Muslim Brotherhood, whose offspring is no one else than Al-Qaeda) into full alliance with Nazi Germany. After his failed pro-Nazi coup in Iraq and Syria he reached Berlin where he met with Hitler and Himmler, who made him an "honorary Aryan". It was the Mufti who insisted on the Jews being killed, not just expelled. In 1943 he created (and was "godfather") of the Bosnian Muslim SS Division, which were sworn in on the Koran, not on Hitler! The SS also had an Islamic school in Dresden.
After the war the Allies pondered about bringing him before trial for war crimes, however he slipped to the Middle East again where many ex-Nazis were finding employment as military advisers in Egypt and Syria. His last prominent activity was organizing aggression against the Israelis. In the 1950's he p*ssed off Arab rulers (who were nationalistic/socialist secular) minded with organizing Islamist radical groups. He died in Lebanon (or Syria... not sure right now) in the 1970's.
The "Keffyieh" (Palestinian "resistance" scarf) is attributed to him during the 1930's Arab revolt.
He was also an relative (some say uncle) of Yassir Arafat.
The ideological groups of him were the base for Al-Qaeda, Fatah, Hamas and Baath. Quite curious that these somewhat "diverse" groups share the Mufti as a common root.
This just as a comprehensive answer... there are several interesting detailed articles on the net on him and his crimes.