I've been having a hard time about this, and so far, this is my conclusion: Let your character be "you".
In my story, what I did is turn my character into an imitation of me, with a bit of some exaggerations. Another thing I did was turn them into humans. Don't turn them into some edgelord Kirito-wannabe with their username XxX-Kirito-XxX or some shitpost like that, but give them something to fear or a weak spot. I won't tell you my character's weakness due to spoilers just for references sake, which is why I mentioned to let your character be an imitation of you yourself. Doing so, it'll be easier to make them realistic. What's their fear? Give them YOUR fear. Their weakness? Give them YOUR weakness. You can make them a bit more exaggerated or something, but hey, this is just my opinion.