Don't know if I've had a "worst."
I don't think I've had any real nightmare cars. Maybe the little '88 Buick Skylark that I'm just trading into from Dad is close -- at least in terms of quality control problems.
Speedometer reads about 25% high. Main odometer reads 093158 -- Always. Trip odo seems to work OK.
Parking brake doesn't work.
Crappy radio has static.
Driver's seat will not sit upright properly, leans too far back. If you lean back hard, it falls over backward.
Hood release cable bad -- presently sticking out of the grille, so you can pull it with pliers.
Headliner was sagging, giving sort of a "canopied bed" appearance. I bought spray headliner adhesive, and fixed it --- or so I thought; it's coming down again.
Rear doors stick, seem to release if you press down on them. Judging by good wine red paint on hood and front doors, but rotten faded paint atop roof and trunk, the car is slightly "bent," due to an old collision repair.
Sometimes the power lock on a rear door doesn't unlock on the first try, so you're never sure if it's really just sticking.
Little hinged "door pull" bar on driver's door came adrift, losing rear hinge pin. We took door apart, put the pin back, put the wire spring back in place, got door back together with minimal damage -- and now I feel that the spring is gone again.
The 2.5 GM four cylinder has a chintzy little oil filter INSIDE the pan. You unscrew a drain that's about five inches in diameter, and the oil COMES OUT. Then you worry the lousy little filter off of the pump pickup line, and carefully push a new on it. When you replace the oversized "plug," it holds the filter in place. I don't see a relief valve in the filter, so don't let it get dirty and starve the engine.
Cutesy full width taillight (probably copied from '67 Thunderbird) has a whole row of little bulbs. You have to remove the whole five foot long taillight to replace them.
Radio has a bunch of those silly little square buttons that apparently fascinated GM in the late 80's and early 90's. Can't tell 'em apart at night.
Glued-on center mirror is gone, though I recently found another.
No gauges except the fuel gauge.
But:
After I replaced a couple of headlights and aimed all four, I can see down the road.
It gets a LOT better gas mileage than our 454 Suburban.
Even though it floats all over the road, and the front strut suspension limits one's choice of shock absorbers, it WILL accept Poly-air bags in the rear coils, and it has conventional shocks on the rear.
The 185/80-13 tires are MUCH cheaper than the rubber on our Suburban.
It does seem to start up and run every time.
It's a "grandpa car," and I'm a grandpa...
I sure will be glad when we get our fordor landau T-bird out of the shop.