Is CO2 Laser the best to use after a subcision?

Lasers  don't lift scars. For this reason, subcision combined with PRP and microneedle radiofrequency are performed to raise the rolling scars. I prefer fractionated low-density CO2 in combination done at the same session. Pre treatment is necessary for darker skin types. A consultation would be necessary to estimate how many sessions are needed. Find a scar expert. Good luck.
Jeff Rapaport MD
Realself All-star

Unfortunately without an image it's difficult to determine what your ideal next step would be. Acne scars need a combination approach for long-term improvement. In my practice, we create a tailored treatment plan for each patient based on their unique scarring.For rolling scars, we typically use soft tissue fillers to plump and lift the scars and build collagen long-term. Next, subcision is used to release the tethered scars that are bound down and depressed due to underlying scar tissue. Lastly, a tailored combination of lasers, peels, microneedling, and fractional radiofrequency or radiofrequency microneedling are used to resurface the skin’s texture. The precise combination of devices is determined based on your skin type, the severity of the scars, anticipated downtime, etc.
We combine all laser treatments with microneedling/PRP to improve the results and accelerate your healing time. Keep in mind that a personalized combination treatment by an expert physician will give you the improvement you're looking for. I recommend getting a formal evaluation with an experienced cosmetic dermatologist and acne scarring expert. Best, Dr. Emer. 

Short answer - if I could have only ONE laser for acne scarring, it would be a short PD powerful CO2 laser. This is ADJUNCTIVE treatment only, the primary is subcision. I conduct BOTH laser and surgical subcision in the one sitting. Acne scar revision comprises of many specialised procedures. For the best results, one should target the acne scar type with appropriate treatments METHODS. Using one or two devices is not optimal. As everyone has a unique pattern of acne scarring, the best solution is a tailored one. Remember, scar revision is a medical procedure that is technical to perform. It is not dependent on the clinic, branch, machine, or laser but by the skill of your dermatologist of plastic surgeon. 
Take for example deep ice pick scars, and narrow box car scars. These are best treated with TCA CROSS and focused angled CO2 fractional laser in low density. Deep narrow scars respond better to this treatment than even the most expensive lasers. On the flip side, rolling, and atrophic acne scars can improve with fractional devices such as Fraxel, fractional lasers, ProFractional erbium lasers, Infiini –Intensif –Intracel radiofrequency microneedling. Atrophic scars (depressions) can be treated with either fat graft, PRP or dermal fillers. Tethered and anchored scars are best treated with surgical techniques such as subcision. Other surgical techniques that I use include punch elevation, surgical elevation, punch excision and traditional excision for focal scars. Early and very mild acne scars respond well to eMatrix and non-energy microneedling, as well as vascular lasers. Skin colour changes such as PIH or dark marks respond best to sun protection, creams, and Q switch lasers in the nano and pico pulse durations. 
In the vast majority of patients, different patterns of acne scars will be present. Monomorphic acne scarring (scars of the safe subtype) are extremely rare. Careful examination, especially under angled lighting with scar mapping will give you an understanding of what are the best options for your scars. Additionally tactile examination namely touch will give me an understanding of the amount of subdermal fibrosis, as special equipment is needed for this sub-set of acne scars.  In the majority of patients its finding the correct combinations that yields the best results. It is never about the device, it is about the specialist behind the equipment that will deliver the best outcomes. 
Global leaders in acne scar revision will always use manual methods to revise scars, and employ lasers and energy devices as instruments to assist. All the best, Dr Davin Lim. Acne scar dermatologist specialist. Brisbane, Australia.