Um... This is a hard one, but I'm going to say The Edge of Glory. It's not really because of the song (which I'm not as crazy about as all the other stans) but just the way it was handled with the transition from Judas to it and the video... Eek.
Cool song, but not what radio needed or wanted during this era of music. Expended all of her hard earned capital.
Also, imparted a religious/political tone for the era... causing Judas to flop. A blasphemous feat in itself.
Yeah, it was only a promotional single. Not an official one that was sent out to radio or anything like that. It's just on a whole different rank from the rest of her singles in my opinion, nothing really spectacular or revolutionary, it was just there.