Cannabis.
It took me
YEARS to admit that the negative (side)effects greatly outweighed the positive.
Very difficult issue for me, and I wasted lots of time with it.
K seems a contender as it can be quite seductive.
It's really a moral issue I believe, as I'm unable to go on a forever binge without feeling ashamed of myself.
That feeling beats the seductive effects, so it's really a non-issue.
I feel 7-12 days intervals are ok and rarely exceed that, and never without a reasonably sound excuse.
But...moot point. Can't find any, nor have I for months.
(lovely new smiley)
Some mention 2C's. I like 2C-B but rarely do it. Non-addictive. Would do it more often if I had K, because I feel the combo is really useful and powerfully amusing too.
Still non-addictive though.
And my vote for the least addictive drug....: MeO-5-DMT
*shiver*