From the photo, it appears that post-inflammatory hyperpigmentation (PIH), i..e. the "footprint" of prior inflammatory acne, is the major problem here. In general, so long as there is no accompanying scarring, most postinflammatory pigmentation, like post inflammatory erythema (PIE)--i.e. redness--will fade spontaneously with time. Usually this takes longer on the chest and back than on the face and longer in people of color than less deeply pigmented individuals. Several weeks to several months are usually required for complete fading (so long as no new acne or folliculitis breakouts occur to set the entire process back).To help speed this process, a series of a variety of in-office superficial peels may be employed, which include low-strength TCA, full strength salicylic acid, Jessners solution and full-strength glycolic acid--all of which I have used for this purpose, either alone or in various combinations. At-home bleaching preparations, which may include hydroquinone in varying concentrations, retinoic acid, arbutin, kojic acid and certain licorice extracts may be used in order to further enhance and expedite the process of fading.In general, I feel that bells and whistles lasers of various kinds and IPL, which are often hyped for treating these kinds of problems, do little more than add to the expense of treatment. Best to see a board certified aesthetic dermatologist who will be best be able to control any active acne, if present, and tailor a treatment regimen for you. Best of luck.