Don't really have a worst... But these are memorably lousy experiences.
Cocaine, then ecstasy
Speed and ecstasy => panic attack, hallucinations
Oral weed and ecstasy => waste of both, drugs seemed to work against eachother, will try again with different timing though.
LSA and ecstasy => waste of both drugs, wasn't pleasant, didn't synergyze
LSA and mushrooms => though I did get something out of the trip... It just didn't seem to synergyze+ annoying nausea/cramps. The LSA seemed to keep the mushrooms from working. All in all the combo felt more like an unpleasant lowdose LSD experience than it felt like either of the drugs.
Too much alcohol, then smoke a joint => puking, feeling like utter shit until you pass out for 12 hours
MDMA, speed and ritalin(in that order, and with alcohol) => terrible stomach pains, tried to puke several times but couldn't, eventually passed out
Alcohol and benzo's => I can't seem to restrain myself from going easy on both the alcohol and the benzo's, always leads to passing out/ forgetting everything that happened
Ketamine and benzo's => waste of ketamine, pretty much the only thing you get from it is discoördination