By “favorite fictional character” I don’t mean “favorite character of your favorite fiction”, consider the media itself to be irrelevant.
Just consider the character itself and how it changes throughout whichever segments of its timeline, regardless of how the world moves around it (unless it’s relevant);
the show / book / comic / game / political campaign itself may be absolute trash, but you love some character from that more than any other character from anything at all.
Like Magnifico from Wish, or the driver from Big Rigs: Over the Road Racing.
I usually can’t decide which is my top pick.
Esme is awesome, the picture of uncompromising competence.
Lord Vetinari, doesn’t like how the world works, but works the world until it is better.
Sam, has such a great character arc.