#1 worst: Jennings .380. It was free, and it blew the side of the chamber/barrel off at less than 50 rounds. Melted it with a torch (incredibly easy).
#2: Springfield GI- USED AND HOME SMITHED. Got it as a bunch of parts for 250$. Rear sights filed past use and falls out, broken ejector leg, broken ejector arm. Holes drilled for rail, Plunger tube leg broken off, different barrel installed that was incredibly poorly fitted. Backyard gunsmiting at its best.
bought a spring and pin kit, new plunger, new extractor. Fitted the barrel the best I could and put a bunch of old 1911 parts I had lying around in it. Shoots reliably with ball now, and Ive got about 300$ in it total.