Violet Parr (voiced by Sarah Vowell) is a junior high school teenager stuck at the crossroads between girl and woman. Violet desperately wants to be like everyone else, to blend in with normal people, and to not stand out. Appropriately, her superpowers allow her to turn instantly invisible, and to generate spherical force fields to protect herself (and also to levitate extremely heavy objects; the interiors of the force fields have an anti-gravitational effect, allowing Violet to levitate inside), but she can be stunned temporarily if the field is struck by a sufficiently large force.
During the movie she and Dash combine their powers to create the IncrediBall (named in the video game), a tactic in which Violet generates a force field around herself, and Dash, uses his speed power to use the ball like a cannonball or battering ram. Her struggle with her shyness and lack of confidence constitutes a major side story in the movie, spurred by Helen's encouragement that she had more power than she realizes and that she just has to believe it, as well as her warning to her and Dash that the villains that they would be confronting are even more merciless than the ones that they used to see on Saturday mornings.
Violet's name alludes to "shrinking violet", which means a shy person (usually a girl) or as a reference to ultraviolet light, which is outside the visible spectrum. The name is also a reference to the violet color of her force fields. Edna Mode designed a sturdy super suit that turns invisible when Violet does (her normal clothes do not) and will not disrupt her force fields. The nature of Violet's powers naturally made the super suit a tricky one to fabricate, but nowhere near the potential challenge of designing a newer, more superpower-friendly super suit for Jack-Jack.