Accutane
The sides are shit, but it's a total and utter acne wonder-drug.
I had it REAL bad at 19, and I was ordered to do it by a dermo, and it cleared the lot.
It was expensive but worth it.
I'm 29 now and I've never had a zit since, except for obviosuly the odd one every 28 days, but not like the shit I had on my face, neck, back, shoulders, and chest (no picnic for a teenage girl I can tell you).
Now you would never know I'd ever had a zit.
But the acne has to be chronic for them to prescribe it to you, well it does in this country.