After all of the events that lead up to KH3, reexaming the past to study the future events has always fascinated me. Especially when it comes to the story of BBS. I came too realize that although the the three heroes manage to stop Xehanort creating the X-Blade, all of them payed a terrible price for their actions and over all effect on the Xehanort Saga.
For those who don't know what a pyrrhic victory is, it is a victory where the costs of achieving said victory was so devastating that is dismisses or hollows out the prospect of satisfaction from the win. Over the course of playing all the character stories and the final episode, the stories of all three of them seem to fall in line with the definition.
Ventus: heart was split and formed his dark counterpart Vanitas, after the power of dues ex Mach---- I mean Sora's heart ( pun on nomura logic) his heart is resorted and becomes full of light. Then is coup up in the land of departure for a couple years in order to built back strength in order to eventually fight with Vanitas. They do merge and fought inside the heart of Ventus/Vanitas until Ventus wins but his hear t becomes severely damaged, leaving him in a cosmatos state u till his heart is repaired by staying within Sora for 10+ years.
Terra: goal of Keyblade master and power obsession catches Master Xehanort attention. His fear of Darkness that lurks inside of him is exploited throughout his journey. Not helping that he accidentally helps some villians and is constantly wronged for trying to do the right thing ( I blame this "trusting idiot" persona on BBS's writing), eventually is played against Eraqus on trump up fear mongering and lies, played a part in his demise, although he defats Xehanort in combat, he gets his body stolen and his lingering Will resided in the Keyblade Graveyard for 11 years until Sora encounters and faces off in combat.
Aqua: despite her well deserved Master status, it causes a rift between Terra and Ventus for different reasons. Mostly played clean up for Terra's or Vetnus's Screw ups. Faced of against both friends at the clash as both were possessed by forces of Darknesses. Her fate becomes somewhat of a short term gain long term loss. Because her saving Terranort ( when Terra was about to break free of Xehanort's control) indirectly caused the invasion of the Heartless, Crearion of Organization 13 and the nobodies, and the Heartless and Nobody of Terranort causing trouble with Sora and his friends. A bit of a slippery slope yes, but not nessecarly a false dilemma.
Master Xehanort said it best " the broken boy who failed to be the blade, the misguided master who sacrificed herself for a friend, and the feckless youth who became my new vessel". Despite there victoies, the costs of achieving them were too high and led to the unfortunate implications leader down the series.