Monogatari series is actually on the easier side to me.. The MC's speed was somehow fast, but the CV said fairly clearly, and most weird terms get explained.
Those with lots of special terms or "dead words" here and there without proper explanation are harder to follow, like Nichijou.
Ah. Well, it doesn't help that most of my Japanese skills come from anime...with no formal training. So stuff like that is kinda hard for me to follow.
I also try to watch with nico comments streaming by. Some kanji are synonymous to some chinese characters (which I've forgotten alot of already), which makes it easier to follow.