Poor balancing between action and story. Load me up with too many pointless battles with villains that exist solely for the purpose of being beaten up, and I'm gonna get sick of it (I'm looking at you, Ninja Scroll series). However, if the series goes for more than two episodes in a row that consist mostly of a lot of blabbity-blabbity, and no action of any kind, I will lose interest very quickly. You need balance, dammit.