A kick to the shin area that will break/disengage and my put creature into prone

Benefits

1. if grappled (must hit AC) will break the grapple and creature needs to do athletics check or goes prone and takes damage as unarmed attack

2. if engaged same as above how ever will be able to disengage without and action

3. if a critical roll is done creature is put in prone and loses initiative and temperately loses 1 to dexterity