Here are some matches where an ATG was shredded at a slam event. I am looking for matches of these greats where they lost some time after they won their first slam title.
The ones that immediately come to my mind are:
2008 FO final: Nadal beats Fed 6-1, 6-3, 6-0
2019 AO final: Djoker beats Nadal 6-3, 6-2, 6-3
1974 Wimbledon final: Connors beats Rosewall 6-1, 6-1, 6-4
2000 USO final: Safin beats Sampras 6-4, 6-4, 6-3
2001 USO final: Hewitt beats Sampras 7-6, 6-1, 6-1
What other matches feature an ATG great getting slaughtered at a slam event? My mind is drawing a blank, since I barely slept last night.