I've tried many supplements, and anti-oxidants, but by far Alpha Lipoic Acid seems to have the most significant impact on my skin out of all of them. When I take it, nearly all of my acne goes away within a few days, with minimal further breakouts, and my skin seems to take on a healthy reddish hue (I am a very pale person). It also gives me a slight relaxed energy boost. I believe it also reduces the appearance of bags under my eyes, but that may be because of the skin hue change.
I also take it with Vitamin E and Vitamin C, since I read that it acts to recycle those in the body - though I'm not sure how true this is. To avoid naming brands, the ALA I take is time released, 600mg in the morning, sometimes an additional 300mg or so at night.
Why does this have such a tremendous effect for me? Immediately it appears to reduce the size of acne, probably through some kind of anti-inflammatory response, but it also accelerates healing of them. Most of my acne is on my upper arms and back, with a few occasional ones on my face region.
I don't believe anti-oxidant activity is enough to explain its effects. I've taken tons of anti-oxidants, and arguably have an extremely anti-oxidant rich diet - acne has always been a thing.