Scratch

Yeah, there's another topic about this, but who cares?

I think my fave is Count Bleck for Super Paper Mario. Spoiler alert, I greyed out the text.
You enter the Void and travel through, fighting O'Chunks and Mimi on the way to Dimentio, who flees through a shortened version of a level from each world, util you return to the Void, commencing Chapter 8-3. You catch up to Dimentio and he says that he is allowing you to aid him to "defeat" Count Bleck. If you ever say yes, it results in an instant game over, causing you to have to restart from the last save point. After you keep saying no, you fight him. You track down Count Bleck, and he is protected by a force field. Eventually the other party members join Mario, and bring Pure Hearts, destroying the shield. He is defeated. New players think this is it, but Dimentio snaps his fingers and Luigi transforms back into his Mr. L self, but without the costume. Sometime before Dimentio snaps his fingers, Nastasia sacrifices herself. A cutscene happens and he becomes vulnerable. Dimentio combines himself with Luigi and the Chaos Heart, and transforms into creepy-creepy Super Dimentio. All worlds soon end around this time. A cutscene happens and he becomes vulnerable.  After defeating Super Dimentio, Bleck and Tippi create the Purity Heart, but this means they must sacrifice themselves. They decide they shall, and they are revealed to be the Timpani and Blumiere mentioned many times throughout the game! They disappear and everybody appears in Flipside. Nastasia wakes up, revealing she is not dead, and there is a touching conversation about whether they are alive or not, and Mimi believes that they are probably in a different world, happy together. Merlon eventually invites everybody off for snacks, as if nothing had happened. Lol!