Kafelnikov versus Stich, Roland Gaross final 1996 was the most embarasing.
Take a look at this parallel between RG 96 and this year:
Kafelnikov in 1996 was in his early 20's, a RG semifinalist a year before who won prior to this title just 2 MM clay tournaments and lost 3 other clay finals.
Let's look at Berdych this year. Mid 20's, RG semifinalist a year before, has won 2 MM clay titles and lost 2 other clay finals.
Stich in 1996 was in his late 20's, a 1 time slam Champion (Wimbledon) in his early 20's, had won 3 clay tournaments and lost 5 other finals.
Let's look at Roddick this year. Late 20's, a 1 time slam champion (US Open) in his early 20's, has won 5 clay tournaments and lost 2 other finals.
Not quite sure how the OP defines "outrageous" as no examples were given except the poll examples of Monaco vs. Granollers in Valencia, but many people seem to have come up with their own interpretation based on lopsided results, surface mismatch, etc.
So I went for most lopsided Slam final result with a young player vs. a much older player.
Just turned 22 year old  Jimmy Connors destroyed an almost 40 year old  Ken Rosewall in the 1974 US Open Final.
Connors won his 3rd major of the year in an hour and 18 minutes with the outrageous score of 6-1, 6-0, 6-1.
Rosewall had just faced Connors in the Wimbledon final that same year and lost 1, 1, & 4.
Rosewall won their first match in the match-up at almost 38 years old in Los Angeles vs 20 year old Connors in 1972, but never won another against the American, losing the last 6 between ages 39-43.
1974 was the first year without a singles title for Ken in an incredible 22 years.
He won 6 singles titles afterwards, including his last title in 1977 in Hong Kong at the age of 43.