as your root user, locate the gnome-shell extensions folder for your regular user;
/home/username/.local/share/gnome-shell/extensions
find the problematic extension and delete it's folder. then login as your regular user, as normal.
alternatively, you could disable all extensions for your user, remove the extension and then re-enable extensions.
to disable all extensions for your reguler user;
su - _username_ gsettings set org.gnome.shell disable-user-extensions true
then after you've logged in and removed the problematic extension;
gsettings set org.gnome.shell disable-user-extensions false
you can also do this via dconf editor or depending on gnome version; gnome-tweaks or via the the 'extensions list' extension.