Yes, I'm not saying I condone what Kain did while he was under Golbez's control, nor am I saying we should disregard what he did because he was under Golbez's control. It happened. It was inexcusable. Not disagreeing there.

But as Heath pointed out, normally he's able to suppress his desires. He likely had thoughts like "I wish I could beat Cecil just to show everyone and especially Rosa that he's not so great". Call it Honour, or morals, or whatever, I'm sure he was then quite capable of going "No, I shouldn't think like that, it's wrong" afterwards. Had Kain been able to leave Mist with Cecil after the earthquake, I doubt he would have betrayed him and Rosa of his own volition. It took Golbez to bring that out of him.

As for Rydia, she was seven. I don't know many seven years old who would recover from PTSD as quickly as she did. Heck, I don't even know many adults who could.