I have not had a "worst" car.

I would say "Bill the Car" was the one with the most character, but all my early cars were at least 12 when I got them, and had plenty of character.
Bill was a 1974 Maverick, light blue, with a brown driver's side door, a black formerly-vinyl roof, which has decomposed and was peeling, maroon primer on the left rear quarter panel, a liberal amount of grey Bondo scattered about, and somewhat religious (holy/holey) floorboard. By the time Bill was slain on a Somerville street one night, (it was slammed into while parked - still ran in an abbreviated-by-a-good-foot form for a month) sky-blue paint had covered the Bondo, so I handed out pieces of Bondo to mourners.

My current car is my Honda CRV, a 2003. It's great - goes up and down hill in snow and ice, gets decent mileage for an "SUV" 26 mpg, is comfortable, roomy and fits lots of stuff! We live on a hill, and there are 4 other CRVs in the surrounding houses.