Hi, I can understand your concern for dark spots on legs that are from chicken pox, insect bites and injuries. After reading your query it appears the possibility of post- inflammatory hyper-pigmentation . These scars are really deep enough to cause visible cosmetic problem especially on face. These are difficult to be treated by any topical medications. We sometimes try different kind of creams for the reduction of the scars. These creams work well for the pigmentation and superficial scarring but for deep scarring we need certain procedures alike scar reversion, punch grafting or by certain lasers. As your scars are pigmented so if I were your dermatologist then would have suggested you to apply certain lightening agents such as kojic acid or Azelaic acid or glycolic acid under dermatological guidance. Do strict sun protection as is the very important factor in causing hyperpigmentaion. Despite above measures if the problem is not getting better then it is better to consult a dermatologist for best guidance. Hope these informations will help.