The computer languages you need to know to become a full stack developer are Javascript, CSS, HTML, Ruby Python, PHP, Postgres, Mysql, Oracle, Nginx, Apache, Ubuntu, Centos and FreeBSD.
You don't have to know all of those languages to become a full stack developer but if you really want to make money as a full stack developer then knowing all those languages and everything above will help you earn a lot more money as a full stack developer since you'll know more programming.