I think, if you want to be the hero in a coding project, you should:

• Never keep your knowledge to yourself, but share your ideas with everyone early on
• Be motivative
• Be on time
• Do not use excuses when things do not work out on your end. Work on a solution instead
• Keep things productive (for ex. try to stop finger-pointing)
• Have a clearly structured work and document all your stuff
• Keep to standards at all times
• Take time to talk to your team about how you do stuff and why you do it that particular way. Take criticism as constructive ideas to improve your work
• Learn. Learn even more. Be the most knowledgeable of them all. But don't brag about it; keep it to yourself and help the others out
• If you do not use agile development methods, try to implement some non-intrusive ones; except if you are the one responsible for the project organization - then be more aggressive about it and find out how you can boost productivity (for ex. (stand-up) meetings with the other developers during which you discuss what you did and what you will do next; use Kanban cards in order to distribute tasks,...)
• Categorize tasks (see this link)

But the most important of them all might be:

This list is not complete!

It's not so much which languages you know. However knowing all the front end like html/css/javascript and then 1 or 2 back end languages such as PHP or java and finally having some experience with databases and servers is where you should sit. Understanding how these work is great and will help you become a full stack developer (FSD). As an FSD or any dev for that matter you must realise that languages/frameworks etc come and go - depending on many factors. It is the ability to analyse and draw conclusions quickly about frameworks/languages that will, in my opinion, make you a great FSD. Recognising which "tool" is best for the job is a much better skill to attain than just learning 1 language or framework.

tl;dr - Have a core understanding of how backend/frontend/servers/databases interact and should work. + the ability to pick the best language/framework for the project at hand.