Make no mistake...I love comics a lot  but on occasion there are some things that just get on my nerves. These are my top 3 pet peeves. 
 
3)  Storyline shifts before a plot's full potential is reached.  

Picture this...You're enjoying a storyline involving your favorite character and waiting for an inevitable showdown with the major villain of the story arc. The tension and build up has been perfect and you're on the edge of your seat waiting for the next issue. It comes but you don't get the resolution that you seek. Instead the storyline has shifted to accomodate a new direction the series is taking. Think One Year Later *Shakes head*.
 
A lot of things can cause this particular problem...a continuity event ala infinite crisis or a change in writing team. Sadly it happens more often than I would like. ^_^; 
 
2) Unnecessary deaths added in for the sole purpose of shock value.
 I sometimes get the feeling that with really big comic book events writers are like " Ok we have an exciting arc in mind...what can we do to make it memorable in our reader's minds? Oh I know...let's find an important character to kill off." *roles eyes*

1) Cover is beautiful but Artwork inside isn't quite as good.
 This one happens a lot. You go to the comic store and see a really beautiful cover introducing the issue and then you open it up and look at the first page and get a nasty surprise.  Growl!