How many endings are there for each slugcat ?

I'd like a list a all the endings for each slugcat, just so that I don't miss anything

Also please don't actually spoil *what's* in the ending, just say how to obtain it

And just for info I'm only at Rivulet rn and have completed all campaigns before that, I just don't know if I did all endings related to all the other campaigns

(I hope that's clear ;-;)