Okay, I'll bite.
One thing that stood out to me was how Nomura himself stated that he saw himself in Xehanort, and used that as a way to construct methods of attacking Sora. I think Xehanort is a massive villain-sue who conveniently has a back-up for whenever his original plans fail. In BBS, the protagonists (Terra and Eraqus specifically) were written to be incompetent as hell to make Xehanort's plans look genius in comparison.
With Terra lacking any real suspicion of a man with obviously malicious intent until it was too late. And there's Eraqus who knew about Xehanort's affinity for the darkness and was even injured by him, but still trusted him. And instead of being rational when learning the truth of Ventus and the x-blade, he tries to kill him, attack Terra trying to protect Ven, and opens himself up to getting finished of by Xehanort.
And then there's KH3 which has Nomura's self-insert murder Kairi, apparently the most important person to Sora, only for him to get a sympathetic send-off from Sora only about an hour or so later. Not to mention Xehanort suddenly having "noble" intentions of resetting this awful universe full of darkness into a better one by using darkness and ruining people's lives. I also would like to bring up how Nomura mentions how he's nothing like Sora and guess what character dies at the end while Xehanort gets to r.i.p. with his strangely forgiving best buddy?