What's best for acne scars... OTC creams like Mederma or scarfade, or RX like tretinions?

Scar improvement. Scar improvement can be achieved, but it takes patience. An overnight improvement is simply impossible. There is no clinical evidence to support Mederma. You need a long peel. This is achieved with tretinoins. Also, microdermabrasion and/or dermabrasion depending on scar depth. A chemical peel is also an otpion, Tretinoins, abrasions, and peels all achieve the desired skin slough. Good luck.