After years of very painful cystic acne, I finally tried Accutane, and it worked. I had the clearest, best skin I could ever remember having. The results lasted, too. I was on it for about 4-5 months, but as soon as I went off it, my skin was so soft, even, smooth and comfortable! That was 15 years ago, and while I notice the occasional zit now, they are not the painful cystic ones and one zit every few months is a lifetime away from the cards I had been previously dealt.
I tried everything under the sun, before Accutane. Everything. Prescriptions, diet changes, topical...the only thing that cleared away (and prevented further) cystic acne -for me- was Accutane. However, it's known to cause birth defects, so DO NOT TAKE IT while pregnant. I'm not sure about nursing, if you plan to do that.
Good luck.