So i have three characters that are going to be "canon" in my own mind. And since i doubt their will be an official canon ending for the civil war i decided to pick one for my own personal thoughts. Now since i have three characters (one thalmor agent, one proud nord, and one proud imperial) one is doing stormcloaks and one is doing imperials. So since im gona say one side won, i want to make one character lose the war, can anyone help me with this?

Well you could disable the essential marker on whichever side you don't like and kill them and pretend like the war is over.