The Rebuild of Evangelion movies.
Sure, they have high production value. Sure, they're legitimately entertaining on a few occasions. That doesn't change the fact, however, that they utterly destroyed everything that I loved about the original series. Everything from the character development to the design of the EVAs is different, and different in ways that, to me, spit on the memory of the original.
I know it sounds like I'm just complaining about the Rebuilds simply because they're different, but if you watch the original series carefully and then watch the Rebuilds with equal scrutiny, you'll see what I mean. The new versions of the characters are crudely written imitations of the originals, the plots of the second and third films move forward by disbelief-shattering turns of events and/or altogether out-of-character levels of stupidity from the characters, several subtle but important (i.e. series-establishing) moments are missing, the EVAs look chubby and bulky rather than powerfully svelte, and so on.
Aside from the Rebuilds, I was absolutely bored out of my mind by K-On! and Hetalia alike. There were also a number of other series of which I only saw one or two episodes before quitting due to how much I disliked them, including Dog Days, Food Wars!, and Ben-To.
