Pontiac Grand Prix
First appeared in 1962 as a full sized two door coupe, similar to the Bonneville. In 1969 it was moved to the mid-sized chassis shared with Chevy's Monte Carlo. Was given a re-style in 1973. Many would agree that 1962-1977 were the most stylish years for this personal luxury coupe. But it was down sized in 1978 to a boxy generic design which continued till 1988. Thats when the Grand Prix was redesigned as a Front Wheel Drive aero jelly bean on wheels. 4 Door models were offered, due to the declining popularity of personal luxury coupes. The Grand Prix lost it's uniqueness and was just another boring GM sedan. It was redesigned in 1997, and 2004, but still continued the same look until the Pontiac name was axed in 2009.
I don't know what GM were thinking in the 80's, but they turned the cool Pontiac Grand Prix into a boring crap box that looked the same as all their other cars.