Skinhead

Skinhead was another member of Biff Tannen's gang from 1955. His nickname stems from the fact that his hair is close cropped in a nearly military crewcut. (Back to the Future)

Original Timeline
At some point before 1955 he, Match, and 3D would befriend Tannen and form a four person gang throughout their high school years. They were forever in trouble with school authorities and were frequent tormentors of George McFly. They were also serious obstacles for Marty Mcfly during his first and second temporal incursions. (Back to the Future Part II)

Biffhorrific Hill Valley
In the hellish alternate reality of the Biffhorrific Hill Valley, Skinhead would serve as a longtime bodyguard of Biff under the employ of BiffCo. As such he would be one of the first to become aware of the existence of Armus and would accompany Biff, along with Match and 3D. (Star Trek: Voyager - Dark Realm)