Nina, a fan favorite, is just as good in Tekken 7 as she ever was. Her fighting style is an amalgamation of two of the weirdest martial arts -- Hapkido and Koppo. It makes her both extremely fast and extremely dangerous, so watch out opponents.
Williams has a few secret attacks in Tekken 7 that mix up really well with her unbreakable grab, such as f,F + 1 + 2 (fast forward + left punch + right punch). And her Rage Art (down + left punch + right punch) is just bonkers: