Back to the topic at hand.
I cannot speak to the "most embarrassing" losses. Embarrassing to who? The players? The fans? I guess I have never personally felt "embarrassed" by the outcome of a sporting event in which I was not a participant. I will say that when I was a junior in high school, my 1600 meter relay team got lapped - that WAS embarrasing!
I can only speak to the most disappointed I've been in the team's performance during my 10 years as a season ticket holder:
2. Michigan - 2003. Oh, what could've been.
5. Wisconsin - 2005. We HAD IT WON
Anyway, that is my list.