To reduce tanning and pigmentation due to acne
1) use a Glycolic acid
2) use a good sunscreen even if staying indoors
3) use Kojic acid
and/ or vitamin c
based creams in morning and potent bleaching cream like hydroquinone
and steroid combination in night( skinlite, melalite etc). As the triple combination cream is potent do not continue beyond a month. In case of redness or irritation stop application. These two creams would reduce pigmentation and would also prepare the skin for optimum results of peels
4) take few sessions of glycolic or TCA peels to regain your constitutive complexion.
Once desirable results are achieved continue sunscreen, avoid sun exposure and may also apply milld pigmentation reducing cream like melaglow.
Hope that answers your query. Take care.