Pagans
The Pagans began as a nonviolent club. However, in the 1970s, leader John "Satan" Marron got the club inveigled with organized crime. Despite their small membership, they are considered one of the most dangerous motorcycle clubs by the Bureau of Alcohol, Tobacco, and Firearms. The Pagans are still around, and they have increased their membership exponentially since their conception.
Back in Time
Motorcycle clubs have existed for over a century. The first motorcycle club was established in 1903, called the New York Motorcycle Club. NYMC merged with other groups to become the Federation of American Motorcyclists. This doesn't;t necessarily mean that members of these clubs are dangerous, it just means that they joined a coalition of like-minded individuals.