Bleach and Naruto. Not so much for their content, but for the way the companies just milk and milk and milk your time away. I once counted an ep of Bleach that was just about 40% flashbacks. Adding all the unnecessary pauses in conversations and action, I would put most of the shows in the 25% - 40% range for pure wasted time. It's obvious they're just streeeeeeeeeeeeeeeetching things as far as they can, and it really trashes the quality of the work.
To be sure, a huge reason is the different pace of manga production vs anime - manga is monthly, anime is weekly, and the studios are in a position where they have to keep the attention of the audience so they can keep the toy sales going. So they can't ever not produce a show for the week.
However, reasons or not, the effect is that those series just suck to watch compared to a show that tells the story straight on through at its natural pace.
To be sure, a huge reason is the different pace of manga production vs anime - manga is monthly, anime is weekly, and the studios are in a position where they have to keep the attention of the audience so they can keep the toy sales going. So they can't ever not produce a show for the week.
However, reasons or not, the effect is that those series just suck to watch compared to a show that tells the story straight on through at its natural pace.