Over the Edge 1999, for obvious reasons. The show shouldn't have continued after Owen's fall, and when it did, the accident overshadowed everything. A fair few of the performers were quite understandably distracted and off-form afterwards.
EDIT: That's obviously 'worst' PPV, to clarify it.
"Well sir, I guess there's just a meanness in this world..." Current Fave Five:
How was Capitol punishment the worst ever? Punk going over Mysterio? Orton vs Christian, Cena vs Heel Truth (cant for the life of me understand why they turned him face!)
It wasnt the best, but the worst? camaaan
December To Dismember.... I was in the audience.... It had potential, but it played out entirely wrong. Sitting in the crowd expecting atleast 75% of what the old ECW was, and only getting maybe 25% of what it was, HURT.