How to remove the Themekey module after its Installation failed? I installed the module ThemeKey, but the installation failed with a WSOD. Now every page gives me the same 'The website encountered an unexpected error'. 

So I need to remove themekey, but how can I do so? The watchdog table doesn't include any message relating to this problem, so is no help. Can I disable/remove it via the database, or am I stuck with rebuilding the whole system?
Use Drush drush pm-uninstall themekey or Drupal Console drupal module:uninstall themekey to disable themekey from the command line.