When it comes to technical skills, a Drupal engineer should have:
A grasp of PHP & PHP Frameworks
Experience working with modules (installing, debugging, developing)
Drupal theming experience (the candidate should know how to create custom Drupal themes)
Experience in debugging and updating Drupal sites
Knowledge of the Software Development Life Cycle
Knowledge of layout grid systems
Also, don’t forget about soft skills, which include communication skills, listening skills, time management, problem-solving, leadership, empathy, and so on.