Estranho, em minha máquina o Opera não é um pacote virtual.
Sem entrar no mérito de pq vc quer desinstalá-lo (eu gosto muito dele, mas no fim, a máquina é sua), tente localizar qual o pacote que instalou o programa:
dpkg-query --search `which opera`
Com o pacote identificado, vc pode mandar desinstalá-lo com um "apt-get purge".
Sugestão:
dpkg-query --search `which opera` | cut -f1 -d':' > /tmp/pkg
sudo apt-get purge `cat /tmp/pkg`
Olha aparece essa mensagem
gnome-user-guide: /usr/share/help/fr/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/pa/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/sv/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/id/gnome-help/accounts-which-application.page
debianutils: /usr/share/man/fr/man1/which.1.gz
gnome-user-guide: /usr/share/help/hi/gnome-help/accounts-which-application.page
language-pack-gnome-pt-base: /usr/share/help-langpack/pt_BR/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/es/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/sr/gnome-help/accounts-which-application.page
app-install-data: /usr/share/app-install/icons/whichwayisup.png
debianutils: /usr/share/man/es/man1/which.1.gz
app-install-data: /usr/share/app-install/desktop/whichwayisup:whichwayisup.desktop
gnome-user-guide: /usr/share/help/te/gnome-help/accounts-which-application.page
debianutils: /usr/share/man/sl/man1/which.1.gz
gnome-user-guide: /usr/share/help/nl/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/vi/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/lv/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/pt_BR/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/ja/gnome-help/accounts-which-application.page
debianutils: /bin/which
gnome-user-guide: /usr/share/help/el/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/sr@latin/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/C/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/gl/gnome-help/accounts-which-application.page
debianutils: /usr/share/man/de/man1/which.1.gz
gnome-user-guide: /usr/share/help/it/gnome-help/accounts-which-application.page
syslinux-common: /usr/lib/syslinux/whichsys.c32
debianutils: /usr/share/man/man1/which.1.gz
gnome-user-guide: /usr/share/help/ru/gnome-help/accounts-which-application.page
debianutils: /usr/bin/which
gnome-user-guide: /usr/share/help/sl/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/ca/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/de/gnome-help/accounts-which-application.page
gnome-user-guide: /usr/share/help/hu/gnome-help/accounts-which-application.page
python2.7: /usr/lib/python2.7/whichdb.py
gnome-user-guide: /usr/share/help/fi/gnome-help/accounts-which-application.page
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/96/opera-extension.png
linux-image-3.2.0-23-generic-pae: /lib/modules/3.2.0-23-generic-pae/kernel/drivers/media/dvb/dvb-usb/dvb-usb-opera.ko
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/64/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/96/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/32/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/24/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/16/opera-widget-manager.png
linux-image-3.2.0-24-generic-pae: /lib/modules/3.2.0-24-generic-pae/kernel/drivers/media/dvb/dvb-usb/dvb-usb-opera.ko
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/48/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/96/opera-browser.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/16/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/24/opera-unite-application.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/32/opera-widget-manager.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/32/opera-extension.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/16/opera-extension.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/22/opera-extension.png
python-twisted-core: /usr/share/pyshared/twisted/test/test_cooperator.py
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/22/opera-unite-application.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/22/opera-widget-manager.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/22/opera.xpm
faenza-icon-theme: /usr/share/icons/Faenza/apps/48/opera.xpm
faenza-icon-theme: /usr/share/icons/Faenza/apps/scalable/opera.svg
python-launchpadlib: /usr/share/doc/python-launchpadlib/docs/operations.txt
faenza-icon-theme: /usr/share/icons/Faenza/apps/96/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/22/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/48/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/64/opera-widget.png
python2.7: /usr/lib/python2.7/lib2to3/fixes/fix_operator.py
faenza-icon-theme: /usr/share/icons/Faenza/apps/64/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/32/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/48/opera-widget-manager.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/16/opera-browser.xpm
python-lazr.restfulclient: /usr/share/doc/python-lazr.restfulclient/docs/operations.txt.gz
faenza-icon-theme: /usr/share/icons/Faenza/apps/24/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/64/opera-widget-manager.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/48/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/16/opera-browser.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/16/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/24/opera-browser.xpm
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/22/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/64/opera-extension.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/48/opera-extension.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/32/opera-unite-application.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/22/opera-browser.xpm
faenza-icon-theme: /usr/share/icons/Faenza/apps/16/opera.xpm
faenza-icon-theme: /usr/share/icons/Faenza/apps/24/opera-browser.png
bleachbit: /usr/share/bleachbit/cleaners/opera.xml
faenza-icon-theme: /usr/share/icons/Faenza/apps/scalable/opera-widget.svg
faenza-icon-theme: /usr/share/icons/Faenza/apps/48/opera-browser.xpm
faenza-icon-theme: /usr/share/icons/Faenza/apps/24/opera.xpm
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/scalable/opera-widget.svg
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/64/opera-unite-application.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/24/opera-widget-manager.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/32/opera.xpm
linux-headers-3.2.0-23-generic-pae: /usr/src/linux-headers-3.2.0-23-generic-pae/include/config/dvb/usb/opera1.h
faenza-icon-theme: /usr/share/icons/Faenza/apps/22/opera-browser.png
python-twisted-core: /usr/lib/python2.7/dist-packages/twisted/test/test_cooperator.py
faenza-icon-theme: /usr/share/icons/Faenza/apps/16/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/24/opera-extension.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/32/opera-browser.xpm
faenza-icon-theme: /usr/share/icons/Faenza/apps/48/opera-browser.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/96/opera-unite-application.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/24/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/scalable/opera-browser.svg
faenza-icon-theme: /usr/share/icons/Faenza/apps/96/opera-widget-manager.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/scalable/opera-unite-application.svg
faenza-icon-theme: /usr/share/icons/Faenza/apps/32/opera.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/16/opera-unite-application.png
linux-headers-3.2.0-24-generic-pae: /usr/src/linux-headers-3.2.0-24-generic-pae/include/config/dvb/usb/opera1.h
faenza-icon-theme: /usr/share/icons/Faenza/apps/32/opera-browser.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/scalable/opera-widget-manager.svg
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/48/opera-unite-application.png
manpages: /usr/share/man/man7/operator.7.gz
faenza-icon-theme: /usr/share/icons/Faenza/apps/22/opera-widget.png
faenza-icon-theme: /usr/share/icons/Faenza/apps/64/opera-browser.png
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/scalable/opera-extension.svg
faenza-icon-theme: /usr/share/icons/Faenza/mimetypes/96/opera-widget.png
O que eu faço agora??