My worst was a 1982 Olds Cutlass Supreme coupe. In its defense, the car was 11 years old and had about 61,000 miles when I bought it, and I only paid $800 for it. It had been old-lady owned, which normally is a good thing, but not if you don't keep up on maintenance, I guess.
About a month after I bought it, the transmission started acting up, holding the gears too long, and shifting rough. I took it to a transmission shop and they said they could clean it out and get it running right for about $150...but couldn't guarantee that the problem wouldn't come back soon. It had metal shavings and debris that were clogging the filter. So, since it was already compromised, chances are it would have kept deteriorating. I thought I was going to keep this car "forever", so I opted instead to have the transmission rebuilt. This was 1993, and it was around $675. Not too bad, I thought.
In early 1994, the car needed new tires. Again, since I thought I was going to keep it for the long haul, I bought fairly nice ones. Then, a few weeks later, it lost all oil pressure. A friend of mine was able to replace the gears in the oil pump for me, but again, like the transmission, there was a lot of metal shavings and such in oil, another sign that sucker wasn't long for this world. Replacing the gears and changing the oil did make the oil pressure light go off, though.
In the end, I sold that sucker, with 73,000 miles on it, for $400. The engine was sounding sicker by the day, so it wasn't going to last much longer, most likely.
The engine it had was a 231-2bbl V-6, manufactured by the Buick division. Ironically, a few years later it would be hailed as one of the most durable engines in production. But, the 1984 and earlier versions had a lot of narrow, right angle oil passages that were easy to clog, and other issues. I've heard one problem was also that the block was a little too lightweight for the time. The auto makers just didn't have the technology yet to reliably produce an engine block that was that lightweight and thin.
Anyway, it was the only car I've ever owned where both the transmission and engine crapped out on me. Still, I liked the car. It was good looking, roomy, comfortable, handled pretty well, and was a good highway car. 0-60 was kind of slow, but at highway speeds it seemed to catch its second wind. It was a light, silvery greenish color called "Jadestone", I think. The landau top and Rally wheels were color coordinated as well.