Arafat was an thoroughly evil man. He used Zionism as an excuse just as Hitler used “lebensraum” as his excuse. By Hitler the real motivation was his war against the Jews. Ditto for Arafat. Hitlerian comparisons are generally unfair and inappropriate but most of us would agree that by Arafat it’s OK.
Regarding the father of modern day terrorism: Arafat is up there but depending on how you define terrorism, he may not be the first. Robespierre from the French Revolution probably qualifies as an early proponent.
Do a google search on The Muslim Brotherhood. This viciously anti-Semetic group was founded in 1928. Its founding principles do not seem to mention Zionism.