I’ll start with the Porsche 997, the 996 looked alright imo, but it looks “like a 90s Porsche”, the 997 made it look sleeker and more modern. Still looks good today.
As for cars that looked worse after a facelift? Maybe the facelifted 6th gen Camaro? The 6th gen looked great pre-facelift, but they did something weird with the headlights and now it looks so-so…
The facelift for the 4th generation Corvette was by all accounts worse. In isolation it’s not that the later 4th Gen cars were necessarily bad looking, is just that every single appearance change they made was worse than the original design.