The eighth and absolutely worst car I've ever owned: a gold 1999 Cadillac Catera. I know that they had problems but I did my research on Carfax. Although it had had troubles when it was new, into and out of the shop constantly, it hadn't had any for several years. I figured that whatever the problem had been it was fixed and bought it.
The problem was not fixed. Every four to six weeks I would come out to a dead battery. I had the car jumped so often that AAA refused to come and jump it for me. I replaced the battery twice. Nothing worked. Something was draining the battery and no one was able to find out what. I eventually came to the conclusion that during those "trouble free" years on the carfax report the vehicle had been garaged and ignored until it was finally sold to a sucker, in this case me.
Just when I was thinking that I would have to rip out every electrical component in the car and replace them all with new ones fate smiled upon me and the car was totaled in a fairly minor accident. I got enough from the insurance company to put a sizable down payment on a new car.
I should note that when the car started up it ran fine. Plenty of power, good handling, nice amenities, and so forth but it was completely unreliable. Live and learn I guess.