Honestly the linearity and the lackluster villains. It's hard for me to go back to FFXIII given how linear it is. Bart has so much potential but he was handle very poorly. Don't even get me started on Jihl. I didn't have any real problems with the actual story. I'm still trying to figure out what's so horrible about it. It's no better or worst than most of the other FF. I see far worst stories than FFXIII's. I didn't feel any real attachment to the cast, but they weren't bad except Hope at least until Chapter 9 or 10. I did like Fang and Lightning. Sazh was alright. I could take or leave Vanille and Snow.