I want to be very specific because I will speak in absolutes.
I have been going to the theatre since 1960 (a national tour of My Fair Lady) and probably have sat through a minimum of 1500 professional productions over the years. Granted I have missed some of the legendary flops like 1600 Penna Ave and Got Tu Go Disco, but I have seen my fair share of disasters.
The Best Little Whorehouse Goes Public still has my vote as the worst thing I have ever seen on a professional stage in 49 years.
Not only was the material badly done and poorly staged, The premise of the show itself was offensive.
Tommy Tune hasn't done a show in town since.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher