Are we talking moments that were disappointing or teams/players that underachieved and
became disappointments?
If it's the latter, a more recent example I can think of is the 2018 Steelers. A team with heaps of talent that just couldn't stop the endless drama off the field. Most of their wins were against poorer teams with last minute flukes and final possession game winning drives. They were 7-2-1 in full control of the AFC North and imploded in the final third of the season to finish 9-6-1, finishing 2nd behind the Ravens (who at one point were 4-5) and missing a WildCard spot.
The Steelers are one of my least favourite teams and at the time I found them more inherently unlikeable than the Pats - so, naturally, I thought it was hilarious. I'm sure Steelers fans were disappointed, though.