1. Al Qaeda Al Qaeda is one of the biggest terrorist groups around the world now led by Ayman al-Zawahiri. This is an extremist Islamic group that was created by Osama Bin Laden and was established in the year 1898. He planned the horrendous September 11 attacks on the World Trade Center. Osama was feared across the globe for his integrated terrorist system and powerful strategies. This group consists of many thousands of people who have gone through years of military training and are situated all over the world. Osama was killed in a US commando action in Abbottabad, Pakistan.