5: Ford Focus
When the final generation of the Focus came out, there was a lot that Ford did right. Its gas efficiency and performance were at the top of its class, but fast forward a few years later and the Focus is one of the worst used cars (via Car and Driver). There are a few reasons for this and it comes down to cost of repairs.

The Focus ST was notorious for transmission complaints among consumers, and this is one of the most costly repairs. When it comes to having a brand new car the last thing that you’d expect is for the transmission to go out on you. But the Focus was experiencing more of these problems than other cars in the same segment.