The Worst headphone i have used is a on the ear headphone with a mic manufactured by a Chinese company by the name of Micro Kingdom it cost only $6 including shipping that i have purchased 3 years ago.
The sound signature was dead flat with non existent bass, mids and highs and also when i adjust the volume with the inline control the sound will actually distort grr.
The sound signature was so dull that my ears fell dead asleep
This online purchase my worst audio product investment ever.
BTW the link advertising that product went dead so i can't find any active links.