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?
I have a 2019 Opel Corsa 1.4, the last one under General Motors. I haven't had too much trouble with it during the past 120.000km. It broke down the first time last summer due to a problem with the throttle body, I got a new one for €130 and now it's fine again.
My next car won't be an Opel because of Stellantis. Their engines are pure crap. My brother in law had a Grandland as a leasecar and had a lot of trouble with it. My mother's side of the family was loyal to Opel for more than 60 year but now I'm the last one who still drives one.