I have a website and trying to do on-page optimization but I don't want to see top 10 competitors I only want to see one competitor as that competitor is always on the google #1 spot for all the keywords im trying to optimize my page for.

No, unfortunately this is not possible right now. Maybe during an eventual software architecture re-design we will allow that, but for now you'll have to look at the competitors within the report and try to imitate their optimization ignoring the score.