Investors may be surprised to learn which big bank performed the worst last year. No, it wasn't Bank of America (BAC 0.16%) or Citigroup (C 1.12%), the most frequently maligned too-big-to-fail banks. Instead, it was Wells Fargo (WFC 0.50%), the nation's fourth largest lender by assets and arguably the most respected of the bunch. In the video below, Fool contributor John Maxfield explains how this irony came to be.