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.
Solid choice, he is a bit flawed in the first game (obsessed with pointing fingers at Saren (admittedly only being 1.05% wrong about him)); but he and Hackett are the OG superiors that have your back rather than constantly second-guessing you.
The latter even set his foot on a terrorist-owned ship, imagine the favors he had to pull in order to do that discreetly just to talk with you in person…
Mass effect had a good line up of really amazing characters.
Controversial opinion, but I feel that all games after the first one were only held up by the characters and worldbuilding - hell, ME2’s plot IS the characters