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 BMW E39 5-series looked considerably better after its 2001 facelift, which is impressive considering how little changed— front bumper, headlights, taillights, and steering wheel.
In my mind, the facelift E39, particularly in M-Sport/M5 form, is one of the best-looking sedans of the late 90’s/early 2000’s. It’s handsome but understated, and it’s aged incredibly well compared to some of the more radically designed 2000’s cars.