You need to be well-versed with the following skills to become a full-stack web developer in 2020:
Front-end technology (HTML5, CSS3, JavaScript)
Third-party libraries (jQuery, LESS, Angular and React JS)
Development Languages (Java, Python, Ruby, .Net, etc.)
Database and cache (MySQL, MongoDB, Oracle, SQL Server)
Basic design ability (UI /UX design)
Server (Apache or Nginx servers)
Version control system (VCS)
Working with API (REST & SOAP)
If you want to become a full-stack developer, check out this Full Stack Developer Course by Intellipaat.