Well, the most important thing of an OC is obviously the name. But you should also add appearance wise. Unless you want to do what I do which is a leave their appearance vague, as this allows, your audience to come up with their own appearance for your character, in a sense, creating them for themselves. But most importantly, if you have to give them a personality, you very well need to make sure their personality is realistic. you want to avoid characteristics such as traits that make them too likable and traits to which if other people criticize it that clearly makes them the bad guy. Your personality traits and even their flaws should focus on nuance
