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.
Flinn from the Tainted Sword - it’s an obscure old dragon lance novel about an old knight fallen into obscurity and a determined squire that still echoes the knight’s old glories. Flinn is deeply flawed but goes through extremely realistic growth during the story. If you have the opportunity to read it I’d highly recommend it.