Final Fantasy Wiki: "During the final battle with Seymour inside of Sin, if Anima is summoned Seymour remarks "You would oppose me as well? So be it!" It is unknown though if Seymour is addressing Anima as a former aeon, or as his mother."
My friend Paige:"Can you imagine fighting the woman who wanted you to become strong in the first place? I reckon Seymour would be immune to pain by that point, though, and just see Anima as he saw everyone else.
Especially since she became a Fayth through her pain and grief. He'd want to end her suffering, I think."
Well, I think that Seymour and Yuna are two separate ways of things turning out. Both were considered Half-Breeds, and didn't get accepted by many of their peers. Their parents wanted the best for them, and died when they were both at such a young age. Two scenarios could come from this:
A) the child becomes strong, and decides to live life to the full while bouncing back from the many troubles life throws at them
B) The child slowly becomes insane, and separates themselves from society - in a sense, being strong, but manipulating their power for the worse.
If you mull this over, Yuna could have easily turned out just like Seymour had she stayed in Bevelle. Luckily, she was guided to Besaid by Kimahri, and found a family within Lulu, Wakka, and Chappu.
Seymour was... always lonely.
The guilt off his mother's death ate him alive, and with nobody to help him deal with it, he eroded."Feel free to add whatever.
Final Fantasy Wiki: "During the final battle with Seymour inside of Sin, if Anima is summoned Seymour remarks "You would oppose me as well? So be it!" It is unknown though if Seymour is addressing Anima as a former aeon, or as his mother."
My friend Paige:"Can you imagine fighting the woman who wanted you to become strong in the first place? I reckon Seymour would be immune to pain by that point, though, and just see Anima as he saw everyone else.