I was inspired to ask this question after rereading my own personal choice, Avengers Unplugged 3. Black Widow and Crystal get dressed up in miniskirts and have a "girls' night out" at a male strip club called, uh, "Bimboyz." Coincidentally enough, it's hero night at the club, and at one point Crystal attracts the attention of a male stripper dressed as Quicksilver.
As a fantastic article on the Avengers Assemble website points out, the comic hits its nadir when Black Widow says "You go, girl!" to Crystal.
Avengers Unplugged as a whole was truly, horribly, abominably bad, and #3 get my vote for the worst Avengers issue ever.
Avengers Vol. 3#76 by Geof Johns was really bad, and a bit confusing. A big what the heck deal with the Jack of Hearts' death. All of Larry Hama's issues come in second.