Not to start the argument up again, but I do have a comment on Ultimecia's motivation. She states while possessing Edea during her speech to the citizens of Deling City (near the end of disc one) of how Sorceresses have been persecuted throughout history. That coupled with the fact of SeeDs persecuting her across time would indeed cause her to get pretty irritated and decide to end it all. Not much of a better excuse to go all nihilistic than many of the other Final Fantasy villains, but she isn't without depth. Of course, this also introduces some other plot holes, but FFVIII isn't really without those, as can be noticed.
That's all.
