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?
An early 2000s Jetta my fiancee bought shortly before we got married. The electronic sensors kept dying throughout the warranty and after and were expensive as hell to replace, a pain in the ass to install becsuse I had to take off 6 parts to get to them, and it had horrendous handling in snowy/icy weather. Got rid of that lemon a year after we were married and replaced it with a 2005 Camry that was super reliable and cheap to maintain for the next 18 years.
The Canrywas still going strong when I traded it in for a truck due to changing needs. Literal opposite of that stupid Jetta.