Except in B5 Sheridan's final gambit was to prove that the Vorlon and Shadows had outlived their mission and had become a cancer on the Galaxy as it is now. And it is one of my favorite moments in SF. Sheridan showed that their argument, and reason for being in the galaxy was moot at this point. I would argue that the catalyst is in the Sheridan role in the end of ME. He stands there and argues that all your actions, experiences, and beliefs are meaningless meaning the roles are reversed making his view the protagonist view and us the antagonist. That is partially why I felt and continue to feel that in the end the Catalyst, and thus, the Reapers won and I, the player, lost. And its one of my least favorite moments in SF or any fiction.