The worst, (and best car) I ever owned was my first... A 93 ford festiva. The thing was a piece of crap but it was bulletproof. Owned it from 50,000km and got it up to 140,000km never had it serviced, never changed the oil or filters. The only thing I ever needed to do on it was the CV joints and wheel bearings in the 3 years I had it. It still ran as well as when I first got it, the thing was indestructible and I tried my hardest to kill it.
worst car for me has to be the rb gemini or the lexcen. Rb looked alright , much like a commie crushed into a small car. no service manuals could be found unless it was an american model book. parts just didnt exist, well the ones i wanted anyway alt was 350 and u couldnt buy one recond, box was playing up so i swapped it for a vn lexcen. lexcen shattered the flex plate within 3 days of having it after i get jusnt 2 days and 600 in new parts for the top end. ended up selling a rebuilt engine for ti for 900 and the car unlicenced with no motor or box and bald tires for 500