I can't uninstall modules with Drush master-branch and almost no data on Google
The problem is not with Drush is with admin_menu. This is a bug on admin_menu not been ready. See more about this - admin_menu has broken d8-beta11 and i cant pm-uninstall

How to solve it ?


  (note, deleting the module rm -r modules/admin_menu and rebuilding
  cache brings the site back)


Source 

Steps by Step Instructions


Open your terminal
Change directory to you root Drupal 8 core
Then remove the admin_menu project and then clear the cache.
rm -rf modules/admin_menu # Remove the directory.
drush cr # This will clear the cache


admin_menu is not ready, I will recommend you to use admin_toolbar for now.