The most difficult type of acne scars to treat are often the ones that are the most deeply embedded into the skin and/or have caused the most dermal trauma.   Icepick acne scarring has taken the mantle as being some of the most difficult to treat, as scars are narrow, oval-shaped, and set deep into the skin. They are often compared to the scarring that can come from scratching at chickenpox too aggressively.