I would have to agree with some of the comments on the 2C-x class. With 2C-B especially, we had a rather large amount of it, and used it daily, multiple times a day in fact (almost exclusively insufflation), taking a day break here and there... That lasted for 3-4 weeks. I'm really ashamed of those times, but I must say it was a blast while it was happening.. Then I had pretty bad 2C-B like hallucinations for a few weeks after, mainly LONG tracers and colors were off or brighter for awhile. Now because of that I would never touch 2C-B again, just kind of feel gross thinking about it..
I also did 2C-E about 5 times in a week the first week I got it, then I haven't really used but once or twice since then.
K, while a dissociative many still consider it psychedelic 'enough' to just kind of lump it all together in a general term (GENERAL). By that I simply mean I can say, I prefer psychedelics and don't really use any other drugs, while lumping K and N2O into there as well).. Anyway, I've never found K to be addictive, but I can see the potential.
I can agree with AMT as well, the first time I used it I re-dosed on the comedown, made for a shitty second comedown. This experience also tainted AMT much in the same way last summer did for 2C-B. However, I'm willing to give AMT another shot, just the nausea at first, and feeling 'toxic' at the end kind of turns me off. -Note- I've used AMT more than a few times, and most every time I get that toxic feeling at the end.
Now I wouldn't really consider any true psychedelic addictive (to me at least), and by true I mean skip the K and N2O for this. I don't like to trip as often anymore, so that kind of prevents me from doing anything too often. In fact I have a decent amount of stuff that I need to try because I've had it for too long and haven't yet, lol.