So, I just had a real gut-punch game in my historical league. Down 9-0 on the road, with 1 out and nobody on in the top of the 8th, my offense staged a stunning comeback. 2 in the 8th inning, then an amazing 9 in the 9th inning (opponent ran out of rested relievers) to take an 11-9 lead.
Then...my closer came in. His first blown save of the year, as he allows 3 runs in the bottom of the 9th to waste the 11-run comeback with 5 outs remaining.

My napping 4-year-old was the only thing keeping me from shouting in agony as it happened.
So, what's your worst "wasted" comeback effort?