This one was mine, a 1998 Mercedes W208. The nice things about it were the cool Mono-Wiper, the engine (supercharged 2,3L M111) and the seats that were perfect for my height. It had a terrible ASR system but came with a LSD, so it was lots of fun in the winter.
The not-so-nice things about it were that the ignition randomly would not recognize the key, a missing catalytic converter, two fist sized rust holes in the front control arms, rust all over the underbody and the absolute worst 6-speed manual transmission I have ever used.
It also had multiple alignments but it didn't take long for the steering-wheel to be off-center again. You could see the tail end "crabbing" in the rear view mirror. There was something very wrong with it, which can probably be attributed to one of the 7 previous owners.
This isn't even counting all minor annoyances like the frameless windows not lowering themselves when you open the doors (that was only a thing after the 1999 model year), the wind noise, the awful interior materials, the broken seat latch in the rear, the trunk lock not working... I could go on for an hour like this.
So anyways, what is the worst car YOU have ever owned?
Was it a pre-96 boxy taurus? Those were excellent for the time and very reliable because they had to be to be competitive. 96 brought the doughy redesign that triggered a decline. It held the top sales figure a little longer, but mainly due to continued fleet sales. The transmission was a weak point, the fuel economy was lacking, and "Taurus" was kind of your father's brand. The redeeming benefit was that the 2000 redesign only changed half the car, so they were quite repairable by having a 10 year run. The door skins are identical for the 3rd and 4th gens.