Books You Shouldn't Have Read, and are Embarassed that You Have Read
Okay, let's look at this angle as well....I'll kick us off with Avengers Forever....12 issues of waiting for something to happen, and it goes nowhere. I can't think of a Kang storyline I like, in fact, but this one took the cake.
Also, I once grabbed a Love and Rockets #1 at a flea market, having heard of its importance in the history of independent comics. I couldn't get halfway through. Used it in a trade with an LCS.
Most of the Beyonder appearances I have encountered were wincingly bad too.