I'd lump them into 3 basic endings as they give unique ending screens: Flee, Save the World, Abandon the World.
There's only one way to flee. You get the option to flee and game ends. Let someone else deal with the parasite. You have a teleport scroll so screw it.
There's only one way to abandon the world. You have to complete the so-called evil ending.
There are four ways to Save the World:
Peaceful: Fight no one, win the debate unanimously. Get an unique reward, don't have to fight parasite.
Fight alone: You really messed up the debate. (Note: fight alone for this includes if your sister is with you or not).
Fight with help: You were mostly convincing in the debate. Someone helps you. Not much. But hey every bit counts.
Fight all: You weren't supposed to be able to do this and survive.
Note: All the Save the World endings seem to have the same ending screen. You leave and watch something blow up.
Also, adding a spoiler tag to the thread just to be careful.