(Aside from building the Bismark, Admiral Hipper and several series of U-Boats), Blohm und Voss also made the Bv138 seaplane. The Bv222 flying boat was awesome in it's own right and still holds several distinctions due to it's size.
The asymmetric Bv141 may not have looked "normal", but it performed well.
I would certainly say there's other aircraft manufacturers that deserve the "worst" title besides Blohm und Voss
I was joking of course, I remember making a model of the Bv 141, I had to look up "Asymmetric" in the dictionary. My vote goes to Blackburn, if a plane looks "right" they usually are. Blackburn never made a plane that remotely looked "right" to my eyes.