Knockback is a straight 'thug' style super-villain, a young lady raised by an amoral mother (herself a super-villain) and gifted with super-strength which she has learned to use with telling effect. The backstory is well-written although gives little reason other than poor parenting for Knockback choosing to be a 'villain. That and sheer greed of course, but the main reason appears to be that the poor girl was never shown the merits of any other life but that of a thief.
Set up as PL12, the stat block is straightforward, and there is a clear and colourful costume sketch. Note the lack of mask, Knockback does not conceal her identity...
... and this leads to a neat twist. Her dad - although he never learned of her existence - was a super-hero called Ironblade... so named because he wielded a magical sword. This sword is still around, it disappeared after he died and it is left up to you where it goes and into whose hands it decides to place itself. This could prove... entertaining.
Knockback is a staunch follower, useful muscle, though unlikely to lead in anything more than a straightforward robbery with violence.