For me, it would be Teen Titans. Not just because I hated the series itself. It was annoying, unfunny, shallow, and a complete mockery of one of my favourite comic series. But more than that, it symbolized a change in the industry to me. Action cartoons could no longer be just action, they needed to have a huge amount of comedy. All cartoons needed to be kid-oriented. Since the series aired, I've noticed most cartoons become shallow and unfunny, tame, and relying on base humour. And besides all this, it was ridiculously popular, just making it worse.
Luckily they've improved within the last year or so, but I still haven't forgiven Teen Titans.
Luckily they've improved within the last year or so, but I still haven't forgiven Teen Titans.