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.