A large mistaken dose of piperazines.
I had (at the time) a high enough MDMA tolerance to triple-drop. There was a breach of trust, a serious enough of a breach that I had forgone testing the pills on the basis of "trust," and I tripled pipes.
To me, that paranoia and sheer self-hate of that comedown was worse than anything meth, speed or any other uppers ever generated.
During those 48 hours, I did a lot of things to distract myself from it all. A lot of those things I can no longer do, as they trigger such a fear. Never, ever did I get that type of continual paranoia, always waiting for you, with meth or other stims.