These are the biggest names when it comes to terrorism in the world right now. And though it is hard to measure power, there can be no doubt that these organizations are striking fear in the hearts of many across the world.
Al-Qaeda is probably the first organization that comes to mind when you think of a terrorist group. Al-Qaeda was first formed in 1989 by Osama Bin Laden and despite the fact that their founder and leader was killed, they still thrive to this day. Their main mission is to bring Jihad on all of the sinners who do not follow the word of Allah. Their biggest act of course was the attack on the World Trade Center in New York City on 9/11.