Velocity

Carin Taylor was the younger sister of Cassandra Lane (the woman who would later become known as Ballistic). As a child, she loved to play baseball and run around with her sister and father. But her father eventually left her mother, and Carin was often beaten by her alcoholic stepfather.

One night when their stepfather was beating their mother, Carin ran from the house at superhuman speed to the nearest police car for help -- the first manifestation of her super-powers. She then raced back to the house only to find that her sister Cassandra had inadvertently killed their stepfather by throwing a comb through his heart. Carin was sent to an orphanage, later being discovered by Nick Fury and brought under training as a SHIELD agent. When Velocity does something, one can be assured it's done fast.