Adderall....hands down, without question the drug that got it's hooks in swim the deepest, although despite this I'm happy to say swim never resorted to meth or crack as I know other upper-seekers have. Swim has an ADD script for it but really he takes it, and has always taken it, for depression and the paradox of it all is that it actually does improve his functionality and quality of life significantly when he can control his intake but for the past 4 or 5 years "abusing" it has been a problem and he's currently still dealing with it. Having plans made for him to go to rehab a couple weeks ago and nearly being sent I think/hope was the final turning point and I think he's actually making progress with the compulsion to over-use because he hasn't since that happened. He's also struggled a bit with benzos but that problem seems to have worked itself out by switching from a short to a long acting form.
I think I'm lucky though in that I never got into opiates like a few of my old friends did because from all accounts addictions to opiates (heroin, OCs, morphine, codeine, other painkillers) are the hardest to kick and swim feels like a pussy sometimes complaining about his problems with Rx psychostimulants. (Quick aside: addiction to nicotine is such a joke compared to previously mentioned dependencies and it bothers me when people complain about being addicted to cigarettes -- I believe it's the availability that makes people believe in the power of that addiction)
I'll be honest, I actually had to look up what spice was when I read this post -- I guess I'm really not up on things -- but I hope you can overcome it; Best of luck. Chemical dependencies are f*cking terrible.