Worst?
Any Polaroid. Land cameras, unreliable exposure, battery hackery, ridiculous prices for manual variants, expired film is a total crapshoot and fresh is now gone but at the time had little options and exorbitant prices.
SX70, hard to find a good working model, ejection issues, terrible to use with glasses, impossible film is very expensive and didn't age all that well, again expired film is total hit and miss now with potential issues with the emulsion, dev pods and battery.
Instant wasn't for me. I just couldnt stomach jumping into a format that required such a high cost to get that larger format look with such little support filmwise.