The best way to improve the look of traumatic facial scars very much depends on location, age and look of the scar. Is the scar thick, thin, jagged, depressed for instance.
Any modality, from surgery, lasers, intense pulsed light to dermabrasion & microdermabrasion
or a combination may be beneficial. It would be best fro you to consult with a facial plastic surgeon with expertise in scar revision