I'm afraid to tell you that he's worst era now is the current one.
His album sales are horrible, true, but he already had two songs hit #1 on the Urban charts, and has a top 10 on the hot 100. I just said that era because of the huge backlash he got from getting married.
Example: "What We Made" era... because he was a total unknown rapper.
Ashlee Simpson: "Bittersweet World" era
Calvin Harris: "I Created Disco" era... but it was pretty succesful in the UK
i'd have to say the one in which she sold million first week!
her debut was flawless, singles did mega awesome and album had the longevity like no other!
fearless .. well it was perfection
so the singles-wise flawed speak now era is her worst!